A 


82S  Broadway 


Xi 


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,oix>«»    REESE   LIBRARY 


UNIVERSITY    OF   CALIFORNIA. 

Received '.._  (2<fte<Zy    , 

Accessions  No.<£%&/^    Shelf. No. 


08- 


•SO 


PRACTICAL 

M ICROSCOPY 

r 

A 
COUKSE   OF  NORMAL  HISTOLOGY 

FOB 

STUDENTS  AND   PRACTITIONERS 

OP 

MEDICINE 


BY 

MAUEIOE    N.   MILLER,   M.D., 

DIRECTOR    OF    THE    DEPARTMENT    OF    NORMAL    HISTOLOGY    IN    THE    LOOMIS 
LABORATORY,   UNIVERSITY  OF  THE  CITY  OF  NEW  YORK 


,      , 

NN^-Xj/  /r^DMlA        ^ 

^^^^j'    -)v\v*\™^,^r 

ILLUSTRATED  WITH  ONE  HUNDRED  AND  TWENTY-SIX  PHOTOGRAPHICAL  REPRODUCTIONS 
OF  THE  AUTHOR'S  PEN  DRAWINGS. 


NEW  YORK 

WILLIAM    WOOD     &    COMPANY 

56  &  58  LAFAYETTE  PLACE 

1887 


Q/VJ55 


COPYRIGHT  BY 
WILLIAM   WOOD   &    COMPANY 


PRESS  OF 

ETTINER,    LAMBERT     A    CO., 
22,    24   &    26   READE  ST., 
NEW  YORK. 


ALFRED  L.  LOOMIS,  M.D.,  LL.D., 

PROFESSOR    OF    PATHOLOGY    AND    PRACTICE    OF    MEDICINE 

MEDICAL    DEPARTMENT    UNIVERSITY    OF    THE 

CITY   OF    NEW   YCM1K,    ETC.,    ETC. 


is 


BY   THE   AUTHOR. 


PREFACE. 


THIS  volume  has  been  prepared  with  a  view  of  aiding  the  instruc- 
tors and  students  of  the  laboratory  classes  which  are  under  my 
direction. 

It  is  also  presented  with  the  hope  that  it  may  be  useful  to  other 
instructors. 

Again,  students  often  wish  to  continue  microscopical  work  during 
the  interim  of  college  attendance ;  to  such,  it  is  my  belief,  these 
pages  will  have  some  value. 

Still  again,  very  many  practitioners,  not  having  had,  during 
pupilage,  advantages  equal  to  those  provided  by  the  modern 
laboratory  equipment,  wish  to  acquire  more  knowledge  of  micro- 
scopy, for  its  value  in  practical  medicine.  To  such  workers,  also, 
I  desire  to  be  useful. 

So  much  technique  has  been  introduced  as  has  been  found  to  be 
of  absolute  necessity,  and  no  more.  The  processes  for  the  prepara- 
tion and  exhibition  of  tissues  are  generally  simple  and  always  prac- 
ticable. 

In  the  description  of  organs,  I  assume  the  student  has  a  fair 
knowledge  of  gross  anatomy,  but  knows  nothing  of  histology.  The 
scheme  or  plan  of  the  structure  is  first  described — using  diagrams 
where  requisite  to  clearness — after  which  the  mode  of  preparing  the 
section  is  indicated,  and,  under  practical  demonstration,  every 
histological  detail  tabulated  in  proper  order.  The  drawings  will, 
I  believe,  aid  in  the  recognition  of  such  elements  in  the  field  of  the 
microscope. 

The  illustrations  are  exact  reproductions,  by  photography,  of  my 
own  pen-pictures  ;  and  distinction  must  always  be  made  between  the 
drawings  which  are  schematic — 'Used  to  emphasize  the  plan  of  struc- 
tures— and  those  drawn  from  the  tissue  as  seen  in  the  microscope. 

Our    literature   abounds   in   excellent  works   for  the   advanced 


VI  PREFACE. 

student,  and  this  volume  is  designed  to  pave  the  way  for  their 
appreciation. 

I  desire  to  record  my  high  appreciation  of  the  aid  of  Drs.  Charles 
T.  Jewett,  Egbert  Le  Fevre,  E.  Eliot  Harris,  Milton  Turnure, 
H.  Pereira  Mendes,  J.  Gorman,  A.  M.  Lesser,  J.  Alexander  Moore, 
Robert  Roberts,  Esq.,  Warden,  and  Mr.  John  Burns,  Clerk  of 
Charity  Hospital,  in  facilitating  my  access  to  valuable  tissue  for 
the  illustrations  and  for  my  own  studies. 

My  thanks  are  due  my  First  Assistant,  Dr.  F.  T.  Reyling,  for  his 
indefatigable  efforts  in  furthering  the  work  ;  and  to  Mr.  A.  J.  Drum- 
mond,  for  photographical  favors. 

MAURICE  K  MILLEfe. 
NEW  YORK,  June  1st,  1887. 


CONTENTS. 


PAGE 

TITLE   PAGE,    DEDICATION,    LIST    OP   ILLUSTRATIONS,    AND    TABLE    OF 

CONTENTS,  .  .  .  .  .  .  .  .       i.  to  xv. 

PART  FIRST. 

TECHNOLOGY. 
THE  LABORATORY  MICROSCOPE. 

DESCRIPTION  OF  THE  STAND,      .......      1 

LENSES,  .........  3 

GENERAL  ADJUSTMENT,    ...  ....      4 

ADJUSTMENT  FOR  ILLUMINATION,     ......  4 

ADJUSTMENT  FOR  Focus,  .......      5 

METHOD  IN  OBSERVATION,      .  .  .  .  .  .  6 

CONSERVATION  OF  THE  EYESIGHT,        .  .  .  .  .  .7 

MAGNIFYING  POWER,  .  .  .  .  .  .  7 

MEASUREMENT  OF  OBJECTS,       .  .  .  .  .  .  .8 

SKETCHING  FROM  THE  INSTRUMENT,  .....          9 

PREPARATION  OF  TISSUES  FOR  MICROSCOPICAL  PURPOSES. 

TISSUE  TEASING,    .           .           .           .           .                      .           .  .9 

SECTION  CUTTING,       ........  9 

FREE-HAND  SECTION  CUTTING,  .           .           .           .           .           .  .10 

CUTTING  WITH  THE  STIRLING  MICROTOME,          .  .  .  .12 

CUTTING  WITH  SCHRAUER'S  MICROTOME,        .           .           .           .  .12 

CUTTING  WITH  THE  AUTHOR'S  MICROTOME,        ....  14 

SHARPENING  KNIVES— HONING  AND  STROPPING,       .           .           .  .16 

PARAFFIN  SOLDERING,            .......  18 

TISSUE  HARDENING,         .           .           .           .           .           .           .  .20 

RAPID  HARDENING  WITH  ALCOHOL,  .  .  .  .  .21 

HARDENING  WITH  MULLER'S   FLUID,    .           .           .           .           .  .22 

HARDENING  WITH  CHROMIC  ACID,  ......  22 

DECALCIFYING  AND  DISSOCIATING,       .           .           .           .           .  .23 

IMBEDDING  AND  INFILTRATING  WITH  BAYBERRY  WAX,            .           .  23 

IMBEDDING  AND  INFILTRATING  WITH  CELLOIDIN,      .           .           .  .24 


Vlll  CONTENTS. 

PAGE 

FREEZING,         .           .           .           ...  .           .           .24 

STAINING  METHODS  IN  GENERAL,        .           .  .           .           .25 

STAINING  WITH  HJEMATOXYLIN,     .           .           .  .           .           .25 

STAINING  WITH  HJEMA.  AND  EOSIN,  .  ,           .           .           .25 

STAINING  WITH  CARMINE,     .           .           .           .  .  .         .           .         26 

STAINING  WITH  CARMINE  AND  PICRIC  ACID,  .           .        ,   .           .27 

STAINING  WITH  SILVER  NITRATE,   .           .  .           .           .         28 

CLEANING  SLIDES  AND  COVERGLASSES,           .  .           .           .           .31 

MOUNTING  METHODS,             .           .                     .  .           .           .         32 

LABELLING  SLIDES,          .           .          .          .  .        -• .           .           .33 

CARE  OF  THE  MICROSCOPE,  .......         34 


PART  SECOND. 
STRUCTURAL  ELEMENTS. 

PRELIMINARY  STUDY. 

s. 

FORM  OP  OBJECTS,          .           .           .          *.           .  .           .35 

MOVEMENTS  OF  OBJECTS,      .           .           .                      .  .           .36 

EXTRANEOUS  .SUBSTANCES,         ,           .           .           .           .  .           .37 

CELLS. 

CELL  DISTRIBUTION,         .           .           .           .           .           *  .           .40 

VARIATION  IN  CELL  FORMS,            .           .           .          .  .           .40 

FLAT  CELLS,         .           „           .           .           .           .          .  "      ...          .41 

SQUAMOUS,  STRATIFIED,  AND  TRANSITIONAL  EPITHELIUM,  ,.          .         41 

PAVEMENT  EPITHELIUM,  .           .          .           .           .           .  ,           .42 

COLUMNAR  EPITHELIUM,        .           .           .          .  • .     '  „  .          ,         44 

CILIATED  COLUMNAR  EPITHELIUM,       *           .           .           ,  .           .45 

SPHERICAL  CELLS,      .           .           .           ...  .          ,         47 

RED  BLOOD-CORPUSCLES,            .           .           .           .           .  .           .47 

BLOOD  PLATES,          .           ..         .           .           .           .  .           .         48 

COLORLESS  BLOOD-CORPUSCLES,           .           .           .  ,           .49 

POLYHKDRAL    CELLS,    .               .               .               .               .     "          .  .               .             49 

STELLATE  CELLS,  .     ,     .    .  '   .     .    .  .   ,     .50 

POLAR  CELLS,  .     .     .     .     ,     .     .  .     .    50 

CONNECTIVE  (FIBROUS)  TISSUES. 

WHITE  FIBROUS  TISSUE,            .           .           .           .           «  .           .51 

YELLOW  ELASTIC  TISSUE,     .           .           .           .           .  .           .         52 

ADIPOSE  TISSUE,  .           .          ,           .           .           .           .  .           .54 

CARTILAGE; 

HYALINE  CARTILAGE,     .           .           .           .           .           .  .           .55 

ELASTIC  CARTILAGE,  ........         56 

FlBRO-ELASTIC    CARTILAGE,             .....  .57 


CONTENTS. 

PAGE 

BONE,  .  .  58 

SPECIAL.  CONNECTIVE  TISSUES. 

ADENOID  TISSUE,  . 

NEUROQLIA,      ...  ....  j> 

EMBRYONIC  TISSUE,         .  .  • 

MUSCULAR  TISSUE. 

62 
NON-STRIATED  MUSCLE,  . 

STRIATED  MUSCLE,      .  ....  6j> 

CARDIAC  MUSCLE,  .  ....•• 

BLOOD-VESSELS. 

/»/» 

ARTERIES,  .  .  .... 

CAPILLARIES,  .  ...  67 

VEINS,  . 

PART  THIRD. 
ORGANS. 

THE    SKIN. 
LAYERS  OR  STRATA, 

HAIRS.       .  •'.'•'•    2 

SUDORIFEROUS  GLANDS,       ..... 
SEBACEOUS  GLANDS,      ...••• 
PRACTICAL  DEMONSTRATION, 

THE    TEETH. 

THE  PULP, 

DENTINE,      ....  • 

ENAMEL, 

CRUSTA  PETROSA, 

PRACTICAL  DEMONSTRATION, 

THE  STOMACH  AND  INTESTINES. 

GENERAL  HISTOLOGY,     . 

THE  STOMACH,          .  j*J 

PRACTICAL  DEMONSTRATION, 

SMALL  INTESTINE, 

PRACTICAL  DEMONSTRATION, 

THE  LUNG. 

BRONCHIAL  TUBES,  .  .  • 

COATS,       .  .  

PRACTICAL  DEMONSTRATION,  ....  yt 

PULMONARY  BLOOD-VESSELS,  .  .  •  •  •      • 


X  CONTENTS. 

PAGE 

THE  PLEURA,           :          .           .           .           .           .           .           .  100 

PULMONARY  ALVEOLI,            .           .           .           .           .           .  .101 

PRACTICAL  DEMONSTRATION,  LUNG  OP  PIG,                .           .           .  103 

PRACTICAL  DEMONSTRATION,   HUMAN  LUNG,          .           .           .  .105 

THE  LIVER. 

•GENERAL  SCHEME,              .           .           ...           .           .  106 

THE  PORTAL  CANALS,             .           .           .           .           .           .  .108 

THE  LOBULAR  PARENCHYMA,                  .           .           .           .           .  109 

PRACTICAL  DEMONSTRATION,  LIVER  OF  PIG,         .           .           .  .110 

PRACTICAL  DEMONSTRATION,   HUMAN  LIVER,          •    «           .           .  113 

PRACTICAL  DEMONSTRATION,  THE  PORTAL  CANALS,        .          >  ..  .114 

PRACTICAL  DEMONSTRATION,  THE  LOBULAR  PARENCHYMA,              .  116 

PRACTICAL  DEMONSTRATION,  ORIGIN  OF  BILE  DUCTS,    .           .  .118 

THE  KIDNEY. 

•GENERAL  DESCRIPTION,      .           .           .           .           .           .           .  120 

THE  TUBULI  URINIFERI,         ,           .           .           .           .           .  .122 

BLOOD-VESSELS,               '   .           .           .           .           .  •        .           .  124 

PRACTICAL  DEMONSTRATION,  with  Low  Power,      .           .           .  .128 

PRACTICAL  DEMONSTRATION,  THE  CORTICAL  PORTION,          .           .  130 

PRACTICAL  DEMONSTRATION,  THE  MEDULLARY  PORTION,          .  .133 

THE  GENITOURINARY  TRACT.   URETER,  BLADDER,  UTERUS, 

VAGINA,  ETC. 

•GENERAL  HISTOLOGY,        .           .           ...          .           .           .  185 

PRACTICAL  DEMONSTRATION,  UTERUS  AND  VAGINA,       .           .  .136 

PRACTICAL  DEMONSTRATION,  PELVIS  OF  THE  KIDNEY,         .           .  140 

PRACTICAL  DEMONSTRATION,  THE  URINARY  BLADDER,              .  .      141 

PRACTICAL  DEMONSTRATION,  URINARY  DEPOSITS,        ...  143 

THE  OVARY. 

PRACTICAL  DEMONSTRATION,  ADULT  HUMAN  OVARY,                .  .      144 

DEVELOPMENT  OF  THE   OVUM. 

PRACTICAL  DEMONSTRATION,  FOETAL  OVARY,              ...  147 

THE  SUPRA-RENAL  CAPSULE.   .           .  .150 

PRACTICAL  DEMONSTRATION,            .        .           .           .           .           .  151 

SALIVARY  GLANDS.     PANCREAS.     PLAN  OF  GLAND    STRUCTURE. 

TYPICAL  GLANDULAR  HISTOLOGY,          .....  153 

TCBULAR  GLANDS,        .           .           .           .           .           .           .  .153 

•COILED  TUBULAR  GLANDS,            .           .           .           .           .           .  154 

BRANCHED  TUBULAR  GLANDS,           .           .           .           .           .  .154 

ACINOUS  GLANDS,           ...              ....  155 

THE  PAROTID  GLAND,  .  ...     157 


CONTENTS.  XI 

PAGE 

SUB  MAXILLARY  GLAND.  .  .  .  .  .  158 

PRACTICAL  DEMONSTRATION,  PAROTID    GLAND,  SUBMAXILLARY  GLAND, 

PANCREAS,  ........      157 

THE  LYMPHATIC  SYSTEM. 

GENERAL  DESCRIPTION,      .......  161 

LYMPH  CHANNELS,       ........      162 

PRACTICAL  DEMONSTRATION,    LYMPH  CHANNELS  OF  CENTRAL  TENDON 

OF  THE  DIAPHRAGM,  .  .          .  .  .  .  163 

LYMPHATIC  NODES  OR  GLANDS,  x    .  .  .  .  .  .167 

PRACTICAL  DEMONSTRATION,  MESENTERIC  LYMPH  NODE,     .  .  169 

THE  SPLEEN. 

SCHEME  OF  ORGAN,  .  .  .  .  .  .  .173 

PRACTICAL  DEMONSTRATION,        .         >.       /    .  .  .  .  174 

THE  THYMUS  BODY. 

•GENERAL  DESCRIPTION,  .  .  .  .  .  .  .177 

PRACTICAL  DEMONSTRATION,         .  .  .  .  .  .  •        178 

THE  NERVOUS  SYSTEM. 

STRUCTURAL  ELEMENTS,         .  .  .  .  .  .  .180 

NERVE  FIBRES,        ........  180 

NERVE  CELLS,  .....  .  .      181 

•CONNECTIVE  TISSUE  OF  NERVE  TRUNKS,          ....  182 

NEUROGLIA,       .........      183 

THE  SPINAL  CORD. 

•GENERAL  DESCRIPTION,       .......  186 

PRACTICAL  DEMONSTRATION,  CERVICAL  SPINAL  CORD,      .  .  .187 

THE  BRAIN. 

MEMBRANES,  .  .  .  .  .  .  .  .  191 

PRACTICAL  DEMONSTRATION,  CEREBRUM,     .  .  .  .  .192 

PRACTICAL  DEMONSTRATION,  CEREBELLUM,        .  .  .  195 

MISCELLANEOUS    FORMULAE,    ETC. 

DAMMAR  MOUNTING  VARNISH,  ......      197 

XYLOL  BALSAM,       .  .  .  .  .  .  .  .  197 

VARNISHES  AND  CEMENTS  FOR  RINGING  MOUNTS  ;  DAMMAR  VARNISH  ; 

ZINC  CEMENT  ;    ANILINE  COLORS  ;    OIL  COLORS  ;    BLACK  VARNISH  ; 

SHELLAC  VARNISH,  .......      197 

PRESERVATIVE  FLUID,         .......  199 

NORMAL  SALT  SOLUTION,         .  .  .  .  .  .  .199 

RAZOR-STROP  PASTE,  .  .  .  .  .  .  199 


Xll  CONTENTS. 

PAGE 

SILVER  STAINING  SOLUTION,    .......      200 

OSMIC  ACID  SOLUTION,       .......  200 

WEIGERT'S  STAINING  FOR  MEDULLATED  NERVE  TISSUE,  .  .  .201 

BAYBERRY  INFILTRATING  METHOD,          .....  201 

KARYOKINESIS,  .........      202 

FIXING  AND  STAINING  CORPUSCULAR  ELEMENTS  OF  BLOOD,  .  .  20S 


LIST  OF  ILLUSTRATIONS. 


FIG.  PAGE 

1.  LABORATORY  MICROSCOPE,            .           .           .           .           .  .2 

2.  COURSE  OF  LIGHT  THROUGH  THE  MICROSCOPE,      ...  3 

3.  FREE-HAND  SECTION  CUTTING,      .           .           .           .           .  .10 

4.  STIRLING  MICROTOME,    .  .  .  .  .  .  .12 

5.  METHOD  OP  IMBEDDING  WITH  PITH,  TURNIP,  ETC.,     .           .  .13 

6.  SECTION  CUTTING  WITH  STIRLING  MICROTOME,       ...  14 

7.  THE  SCHRAUER  MICROTOME,         .           .           .          .           .  .14 

8.  THE  AUTHOR'S  LABORATORY  MICROTOME,    ....  15 

9.  METHOD  OF  HONING  RAZOR,        .           .           .           .           .  .17 

10.  TURNING  THE  RAZOR  ON  THE  HONE,           ....  17 

11.  PARAFFIN  SOLDERING  WIRE,        .           .           .           .           .  .18 

12.  CEMENTING  HARDENED  TISSUE  TO  CORK,     ....  19 
18.  NEEDLE  FOR  HANDLING  SECTIONS,   COVERS,  ETC.,     .           .  .20 

14.  DIAGRAM  ILLUSTRATING  STEPS  IN  STAINING  WITH  H^EMA.,       .  25 

15.  DIAGRAM    ILLUSTRATING    STEPS    IN  STAINING    WITH    H^EMA.    AND 

Eosm,       .           .           .           .           .           .           .           .  .26 

16.  DIAGRAM    ILLUSTRATING    STEPS    IN   STAINING    WITH    BORAX-CAR- 

MINE,   .........  26 

17.  SECTION  LIFTER,       .           .           .           .           .           .           .  .32 

18.  APPEARANCE  OF  BALSAM  MOUNTED  SPECIMEN,       ...  33 

19.  MODE  OF  HANDLING  COVER-GLASS,          .           .           .           .  .32 

20.  DIAGRAM  SHOWING  EFFECT  OF  OIL  AND  AIR  GLOBULES,           .  36 

21.  EXTRANEOUS  SUBSTANCES— HAIRS,  ETC.,  .           .           .           .  .37 

22.  EXTRANEOUS  SUBSTANCES— STARCH,  ETC.,      .           .  38 

23.  ELEMENTS  OF  A  TYPICAL  CELL   .           .           .           .           .  .39 

24.  STRUCTURE  OF  A  CELL-NUCLEUS,       .  .  .  .  .40 

25.  SQUAMOUS  CELLS  FROM  SALIVA,  .           .           .           .           .  .41 

26.  PAVEMENT  EPITHELIUM,            ......  42 

27.  FROG'S  MESENTERY— SILVER  STAINING,  .           .           .           .  .43 

28.  COLUMNAR  CELLS  FROM  INTESTINE,   .           .           ...  45 

29.  CILIATED  CELLS  FROM  BRONCHUS,           .           .           .           .  .46 

30.  DIAGRAM  SHOWING  ORGANS  OF  THE  OYSTER,        ...  46 

31.  CORPUSCULAR  ELEMENTS  OF  HUMAN  BLOOD,   .           .           .  .47 

32.  DIAGRAM.    HUMAN  RED-BLOOD  CORPUSCLE  IN  PROFILE,  .           .  48 

33.  BLOOD  PLAQUES       .           .           .           .           .           .           .  .49 

34.  GLANDULAR  CELLS  FROM  LIVER,       .....  50 


XIV  LIST    OF    ILLUSTRATIONS. 

FIG.  PAGE; 

35.  FlBRILLATED    CONNECTIVE    TISSUE,  .  .  .  .  .52 

36.  YELLOW  ELASTIC  TISSUE,        ......  53 

37.  TRANSVERSE  SECTION  OF  LIGAMENTUM  NUCH^,          .           .  .    53 

38.  CELLS  CONTAINING  FAT,           ......  55 

39.  ADIPOSE  TISSUE  FROM  OMENTUM,            .           .           ...  .55 

40.  HYALINE  CARTILAGE  FROM  BRONCHUS,  56- 

41.  FIBRO-CARTILAGE  FROM  INTERVERTEBRAL  Disc,          .           .  .57 

42.  ELASTIC  CARTILAGE  FROM  PINNA  OF  Ox,  .  .  .  .57 

43.  BONE — SHOWING  LAMINATED  STRUCTURES,        .           .    •       .  .58 

44.  BONE — SHOWING  HAVERSIAN  SYSTEMS,  59- 

45.  CONTENTS  OF  HAVERSIAN  CANALS,         .           .           .           .  .60 

46.  CONTENTS  OF  BONE  LACUNA,  ......  60 

47.  BLADDER  OF  FROG — SHOWING  NON-STRIATED  MUSCLE,          .  .    62. 

48.  DIAGRAM— ILLUSTRATING     STRUCTURE    OF     STRIATED     MUSCULAR 

FIBRE,  .  .  .  .  .  .  .  .  .63 

49.  STRIATED  MUSCULAR  FIBRE  FROM  TONGUE,      .  .  .  .64 

50.  CARDIAC  MUSCULAR  FIBRE,      .  .  .  .  .  .65 

51.  ARTERY  IN  TRANSVERSE  SECTION,          .  .  .  .  .66- 

52.  BLOOD  CAPILLARIES,  .  .  .  .  .  .         67 

53.  LAYERS  OF  THE  EPIDERMIS,         .  .  .  .  .  .69' 

54.  STRUCTURE  OF  THE  DERMA,    .  .  .  .  .  .70' 

55.  HAIR  IN  TRANSVERSE  SECTION,    .  .  .  .  .  .71 

56.  HAIR  FOLLICLE,  .  .  ,  .  .  .  .  .72 

57.  SUDORIFEROUS  GLAND,  ,  .  .  .  .  .73 

58.  SEBACEOUS  GLAND,         .......         73 

59.  SKIN  IN  VERTICAL  SECTION,         .  .  .  .  .  .75 

60.  HUMAN  CANINE  TOOTH  IN  VERTICAL  SECTION,      .  .  .79 

61.  FANG  OF  TOOTH  IN  TRANSVERSE  SECTION,       .  .  .  .82 

62.  STOMACH.    DIAGRAM,      .......         83 

63.  CARDIAC  GASTRIC  GLANDS,  .  .  .  .  .  .85 

64.  PYLORIC  GASTRIC  GLANDS,      .  .          ..  .  .  .         86 

65.  STOMACH  OF  DOG,  .  ..  .  .  ,  .  .  .87 

66.  DIAGRAM  ILLUSTRATING  INTESTINAL  SECRETION,    .  .  .         89» 

67.  DIAGRAM  OF  INTESTINAL  ABSORPTION,  .  .  .  .  .90 

68.  SMALL  INTESTINE  WITH  PEYER'S  LYMPHATICS,       .  .  .92 

69.  BRONCHIAL  TUBE  ARRANGEMENT,  .  .  .  .  .94 

70.  BRONCHIAL  TUBE — SMALL,        ......         96 

71.  BRONCHIAL  TUBE— MEDIUM,          .  .  .  .  .  .98 

72.  PULMONARY  LOBULE — PERSPECTIVE,  .  .  .  .  .101 

73.  PULMONARY  LOBULE— LONGITUDINAL  SECTION,  .  .  .101 

74.  PULMONARY  ALVEOLUS— CAPILLARIES  FILLED,       .  .  .        102 

75.  LUNG  OF  PIG,          ........  103 

76.  PULMONARY  ALVEOLUS  SHOWING  LINING,    ....        104 

77.  LIVER.    DIAGRAM  ILLUSTRATING  PLAN  OF  STRUCTURE,         .  .  107 

78.  GLANDULAR    CELLS    IN    CONNECTION   WITH    BLOOD-VESSELS    AND 

DUCTS,  ........        109- 

79.  LIVER  OF  PIG,         .  .  .  .  .  .  .  .111 

80.  HUMAN  LIVER — Low  POWER,  .  .  .  .  .  .114 

81.  PORTAL  CANAL,        .  .  115. 


LIST    OF    ILLUSTRATIONS.  XV 

FIG.  PAGE 

82.  HEPATIC  CELLS— DETACHED,    .  .  .  .  .117 

83.  HEPATIC  LOBULE  IN  TRANSVERSE  SECTION,      .  .  .  .us 

84.  BILE  CAPILLARIES — ORIGIN  OF  BILE  DUCT,  .  .  .        119 

85.  KIDNEY— DIAGRAM  ILLUSTRATING  PLAN  OF  STRUCTURE,      .  .  121 

86.  KIDNEY  TUBULES — ISOLATED    ......        123 

87.  BLOOD-VESSEL  ARRANGEMENT  IN  KIDNEY,        .  .  .  .135 

88.  KIDNEY— Low  POWER,  .......        128 

89.  KIDNEY — CORTEX  IN  VERTICAL  SECTION,  .  .  .  .130 

90.  KIDNEY— MEDULLA  IN  LONGITUDINAL  SECTION,      .  .  .132 
01.  KIDNEY— MEDULLA  IN  TRANSVERSE  SECTION,  .           .           .  .133 

92.  UTERUS  WITH  VAGINAL  eul-de-sac,   .....  136 

93.  EXTERNAL  UTERINE  Os,    .           .           .           .           .           .  .13$ 

94.  VAGINAL  EPITHELIUM,  .           .           .           .           .           .           .  139 

95.  EPITHELIUM  OF  URETER,    .           .           .           .           .           .  .140 

96.  EPITHELIUM  OF  URINARY  BLADDER,  .....  142 

97.  EPITHELIUM  FROM  URINARY  DEPOSIT,    .....  143 

98.  OVARY — ADULT,  .           .           .           .           ...           .           .  145 

99.  OVARY— FCETAL,       .           .           .            .           .           .  .148 

100.  SUPRARENAL  CAPSULE — Low  POWER,  .  .  .  .151 

101.  SUPRARENAL   CAPSULE — HIGH  POWER,  .....  152 

102.  SIMPLE  TUBULAR  GLAND,         ......        153 

103.  COILED  TUBULAR  GLAND,  .  .  .  .  .  .  .154 

104.  BRANCHED  TUBULAR  GLAND,  ......        155 

105.  DILATED  TUBULAR   GLAND,  ......  156 

106.  PAROTID  GLAND,  .  .   '  .  .  .  .        156 

107.  SUBMAXILLARY  GLAND,       .......  157 

108.  PANCREAS,  .  .  .  .  .'  .  .158 

109.  PERIVASCULAR  LYMPH  SPACES,    ......  162 

110.  LYMPHATICS    OF    CENTRAL    TENDON    OF    THE    DIAPHRAGM— Low 

POWER,  ........        165 

111.  LYMPHATICS    OF    CENTRAL    TENDON    OF    THE    DIAPHRAGM— HIGH 

POWER,     .  .  .  .  .  .  .  .  .166 

112.  LYMPH  NODE— DIAGRAMMATIC,  .  .  168 

113.  MESENTERIC  LYMPH  NODE — Low  POWER,         .  .  .  170 

114.  MESENTERIC  LYMPH  NODE — HIGH  POWER,  .  .  .  .171 

115.  BLOOD-VESSEL   ARRANGEMENT  IN  THE  SPLEEN,  .  .  .  173 

116.  SPLEEN,      .........        175 

117.  THYMUS  BODY,         .  .  .  .  .  .  .  .178 

118.  NERVE  FIBRE,      .  .  .  .  .  .  .180 

119.  CONNECTIVE  TISSUE  OF  NERVE  TRUNK,  .....  182 

120.  CONNECTIVE  TISSUE  OF  BRAIN,          .....        183 

121.  SPINAL  CORD— DIAGRAM,    .  .  .  .  .  .  .185 

122.  CERVICAL  SPINAL  CORD— TRANSVERSE  SECTION,     .  .  .        188 

123.  ANTERIOR  CORNU  OF  GRAY  MATTER— CERVICAL  SPINAL  CORD,      .  189 

124.  CEREBRUM,  .  .  .  .  .  .  .  .193 

125.  CEREBELLUM— Low  POWER,          ......  194 

126.  CEREBELLUM — HIGH  POWER,    ......        195 


PRACTICAL   MICROSCOPY, 


PAKT  FIRST. 


TECHNOLOGY. 


THE  LABORATORY   MICROSCOPE. 

THE  histologist  should  be  provided  with  a  microscope,  in  which 
the  principal  features  of  the  laboratory  instrument,  Fig.  1,  are 
embraced. 

The  body  A,  which  carries  the  optical  parts,  is  made  of  two  pieces 
of  brass  tubing,  one  sliding  within  the  other  and  providing  for  alter- 
ations in  length.  The  objectives,  C,  D,  are  attached  to  the  body  by 
means  of  the  angular  carrier  E.  The  carrier  is  so  pivoted  that  either 
objective  may  be  turned  into  the  optical  axis,  at  will.  The  eye-piece, 
F,  slips  into  the  upper  part  of  the  body,  with  but  little  friction,  so 
that  it  may  be  quickly  and  easily  removed. 

The  coarse  or  quick  adjustment  for  focussing  consists  of  a  rack  Gr, 
which  is  attached  to  the  body,  and  into  this  gears  a  small  (concealed) 
pinion  turned  by  the  milled-head  H. 

The  fine  steel  screw  1,  by  means  of  which  the  more  delicate  adjust- 
ments for  focussing  are  accomplished,  terminates  below  in  a  hardened 
point,  which  impinges  upon  one  end  of  a  lever  (concealed  in  the  arm) 
the  fulcrum  of  the  same  being  indicated  at  the  point  J.  The  oppo- 
site end  of  the  lever  is  inserted  in  a  notch  in  the  split  arm  K.  By 
turning  the  milled-head  L,  the  lever  is  moved,  and  the  optical  body 
raised  or  lowered  with  extreme  delicacy. 

The  sfage,  upon  which  objects  are  placed  for  examination,  is  per- 
forated at  M,  and  a  rotating  disc — not  indicated  in  the  drawing — 
1 


PRACTICAL    MICROSCOPY. 


enables  one  to  alter  the  size  of  the  opening  at  will.     Below  the  stage 
an  arm  may  be  seen  which  carries  a  fork  supporting  the  mirror  N. 

The  whole  is  supported   on   a   short,  stout  pillar  rising  from  the 
foot  0. 


FIG.  1. — THE  LABORATORY  MICROSCOPE. 

This  instrument  was  designed  and  constructed  for  the  laboratories  of  the  New  York  University 
Medical  College.  It  is  strongly  built;  the  mechanism  is  simple;  and  the  height— 10^  inches— 
not  too  great  for  use  in  the  vertical  position. 


LENSES   OF  THE   MICROSCOPE. 

Fig.  2  shows  the  arrangement  of  lenses,  including  a  high-power 
objective  of  the  Wenhain  construction. 

The  objective  A  is  provided  with  one  simple  and  two  compound 
lenses.  The  lens  B,  nearest  the  object,  and  the  one  upon  which  the 
magnifying  power  mainly  depends,  is  an  hemisphere  of  crown  glass. 
Such  a  figured  glass  possesses  both  chromatic  and  spherical  aberration 
in  high  degree.  These  faults  are  corrected  by  the  compound  flint  and 
crown  lenses,  C  and  D,  placed  above  the  hemispherical  glass. 

The  eye-piece  consists  of  two  crown  glass,  plano-convex  lenses,  with 


LENSES    OF    THE    MICROSCOPE. 


their  plane  surface  upward.  The  lower,  E,  is  known  as  the  field-lens, 
the  upper,  F,  as  the  eye-lens.  Eye-pieces  add  very  materially  to  the 
magnifying  power  of  the  instrument,  and  are  constructed  of  various 
strengths  depending  upon  the  curvature  of  the  lenses.  They  ar& 


FIG.  2.— DIAGRAM  SHOWING  THE  RELATION  OF  THE  OBJECTIVE  TO  THE  EYE-PIECE. 


named  according  to  power,  A,  B,  C,  etc.     The  medium,  B,  is  more 
commonly  employed. 

The  microscope  previously   described  stands,   with  the  draw-tube 
in  place,  about  ten  and  one-half  inches  high;  and  represents  the  in- 


4  PRACTICAL    MICROSCOPY. 

struments  used  in  the  New  York  University  Laboratory  of  Biology 
and  Pathology.  They  were  constructed  by  Schrauer,  of  this  city, 
costing  about  fifty-five  dollars  each.  They  are  provided  with  a  single 
eye-piece,  and  Hartnack  objectives  Nos.  2  and  7,  giving  from.  30  to 
400  diameters.  Such  an  instrument  is  well  adapted  to  the  work  of 
normal  and  pathological  histology,  though  a  condenser  *  should  be 
attached  below  the  stage  and  in  the  optical  axis  for  high-power  work 
with  immersion  lenses,  and  especially  for  bacteriological  research. 
The  stand  is  a  rigid  one,  and  if  the  height  of  the  table  upon  which  it 
is  placed,  and  the  chair  of  the  observer  be  in  a  proper  relation,  no 
discomfort  need  be  experienced  in  using  the  microscope  in  the  verti- 
cal position. 

ADJUSTMENT   OF   THE   MICROSCOPE. 

The  microscope  should  be  placed  in  front  of  the  observer,  on  a 
table  of  such  height  that,  when  seated,  he  may,  by  slightly  inclining 
the  head,  and  without  bending  the  body,  bring  the  eye  easily  over  the 
eye-piece.  The  slightest  straining  of  the  body  or  neck  should  be 
avoided.  The  light  should  always  be  taken  from  the  side,  and 
it  matters  little  which  side.  Clouds  or  clear  sky  serve  as  the  best 
source  of  light  for  our  present  work.  Always  avoid  direct  sunlight. 
If  artificial  illumination  be  employed — though  it  is  not  advised  for 
prolonged  investigation — a  small  coal-oil  flame  may  be  tempered  by 
blue  glass. 

ADJUSTMENT   FOR   ILLUMINATION". 

It  will  be  observed  that  there  are  two  mirrors  in  the  circular  frame 
below  the  stage — one  plane  and  the  other  concave.  The  latter  will 
be  employed  almost  exclusively  in  the  work  of  this  volume ;  and  its 
curvature  is  such  that  parallel  rays,  impinging  upon  its  surface,  are 
focussed  about  two  inches  from  the  mirror.  It  will  also  be  noticed 

*  A  non-achromatic  condenser,  after  the  formula  of  Abbe,  of  Jena,  is  in 
quite  general  use  in  this  country.  Its  value  has  been  very  markedly  increased 
here  by  the  addition  of  a  rack-and-pinion  motion.  In  use  for  high  power  work 
with  tissues,  it  is  first  placed  so  that  the  plane  surface  of  the  upper  lens  is  in  con- 
tact with  the  under  surface  of  the  glass  slip  holding  the  object  to  be  exam- 
ined. Light  is  then  reflected  into  the  condenser  as  usual,  excepting  that  the 
plane  mirror  is  employed.  This  will  give  a  strong  illumination,  but  too  diffuse 
for  tissues.  The  light  is  then  modified  by  diaphragms,  or  by  racking  the  con- 
denser downward  until  the  best  effect  is  secured.  For  bacterial  search  the 
strong  illumination  is  employed.  This  gives  prominence  to  the  stained  mi- 
crobes, as  the  other  elements  in  the  field  are  lost  in  the  excess  of  diffuse 
light. 


ADJUSTMENT    FOE    FOCUS.  5 

that  the  bar,  carrying  the  mirror-fork,  may  be  made  to  swing  the 
mirror  from  side  to  side.  The  work  which  we  are  about  to  under- 
take is  of  such  a  character  as  to  require  the  avoidance  of  oblique  il- 
lumination. We  must,  therefore,  keep  our  mirror-bar  strictly  in  the 
vertical  position.  If — the  mirror-bar  being  vertical — a  line  be  drawn 
from  the  centre  of  the  face  of  the  mirror,  through  the  opening  (dia- 
phragm) in  the  stage,  passing  on  through  the  objective,  and  so  con- 
tinued upward  through  the  body  and  the  eye-piece,  such  a  line  would 
pass  through  the  optical  axis.  The  centre  of  the  face  of  the  mirror 
must  be  in  this  axis.  If,  then,  having  gotten  the  mirror-bar  properly 
fixed  once  for  all,  the  light  from  the  adjacent  right  or  left  hand 
window  impinges  upon  the  concave  surface  of  the  mirror,  and  the 
latter  be  properly  inclined,  the  rays  will  pass  through  the  diaphragm 
in  the  stage,  and  become  focussed  a  little  above  the  same.  The  light 
rays  will  afterward  diverge,  enter  the  objective,  and  finally  reach  the 
eye  of  the  observer. 

The  field  of  view  (as  the  area  seen  in  the  microscope  is  termed)  we 
will  suppose  to  have  been  properly  illuminated — and  by  this  I  mean 
that  it  presents  as  a  clear,  evenly  lighted  area.  Turn  all  the  factors 
spoken  of  out  of  adjustment,  and  proceed  to  readjust.  Observe  that, 
if  the  mirror  be  turned — not  swung — slightly  out  of  proper  position, 
one  side  of  the  field  will  appear  dim  or  cloudy  :  this  must  be  corrected, 
and  the  student  must  practise  until  this  adjustment  becomes  easy  of 
accomplishment.  Then  proceed  to  the 

ADJUSTMENT   FOE   FOCUS. 

Observe  that  the  largest  opening  in  the  stage  diaphragm  is  in  the 
optical  axis.  Swing  the  low-power  objective  into  use,  and  rack  the 
tube  up  or  down  until  it  is  about  one  inch  from  the  stage. 

Place  a  mounted  object  upon  the  stage  (a  stained  section  of  some 
organ — say  kidney — will  be  preferable).  Examine  the  field  through 
the  eye-piece,  and  it  will  be  found  obscured  by  the  stained  object,  and 
perhaps  a  dim  notion  of  figure  may  be  made  out.  Eack  the  body 
down  carefully,  watching  the  effect.  The  image  becomes  more  and 
more  distinct  until,  at  a  certain  point,  the  best  effect  is  secured.  The 
object  is  in  focus. 

Note  carefully  the  distance  between  the  object  and  the  objective 
(with  the  Hartnack  No.  2  this  will  be  about  seven-eighths  of  an  inch), 
and  hereafter  you  will  be  able  to  focus  more  quickly. 

Having  observed  the  details  of  structure  as  shown  with  the  inch 
objective,  swing  the  high  power  into  use.  Rack  the  tube  down,  until 
the  objective  is  about  one-eighth  of  an  inch  from  the  glass  covering 


6  PRACTICAL    MICROSCOPY. 

the  object.  The  field  is  much  obscured.  Watching  the  effect 
through  the  eye-piece,  rack  the  tube  down  with  great  care  until  the 
image  appears  sharp.  Note  the  distance  with  this  objective  as  before 
with  the  low  power,  probably  about  one  thirty-second  of  an  inch. 
Then  endeavor,  by  slight  alterations  in  the  inclination  of  the  mirror, 
to  increase  the  illumination.  Turn  the  diaphragm  so  that  the  light 
passes  through  a  small  opening,  and  note  the  improvement  in  defini- 
tion. The  rule  is  :  The  higher  the  poiver,  the  smaller  the  diaphragm. 

You  have  doubtless  observed,  before  this,  that  you  cannot  control 
the  focussing  as  easily  as  when  the  low  power  was  in  use.  Slight 
movements  of  the  rack-work  produce  marked  changes  in  definition  ; 
and  it  is  difficult,  with  the  coarse  adjustment  alone,  to  make  as 
slight  movements  as  you  may  desire.  Recourse  must  be  had  to  the 
fine  adjustment. 

Place  the  tip  of  the  forefinger  (either)  upon  the  milled-head  of  the 
fine  focussing-screw,  and  the  ball  of  the  thumb  against  its  side,  so 
that  the  hand  is  in  an  easy  position.  By  a  little  lateral  pressure  the 
milled-head  may  be  turned  slightly  either  way.  Note  the  effect  on 
the  image.  You  thus  have  the  focussing  under  the  most  perfect  con- 
trol. 

Remember  that  the  fine  adjustment  is  only  necessary  with  high 
powers,  and  then  only  after  the  image  has  been  found  with  the  coarse 
adjustment. 

METHOD    IN   OBSERVATION. 

The  study  of  objects  under  the  microscope  should  be  conducted 
with  order  or  method. 

The  body  being  in  the  position  before  advised,  so  that  the  sitting 
may  be  prolonged  without  fatigue,  let  one  hand  be  occupied  in  the 
maintenance  of  the  focal  adjustment.  It  will  be  found,  however 
flat  an  object  may  seem  to  the  unaided  eye,  that  as  it  is  moved  so  as 
to  present  different  areas  for  examination  (and  with  the  higher 
powers  only  a  small  area  can  be  seen  at  once)  constant  manipula- 
tion with  the  fine  adjustment  will  be  required.  It  will  also  be  found 
that  even  the  various  parts  of  a  simple  histological  element — like  a 
cell — cannot  be  seen  sharply  with  a  single  focal  adjustment.  The 
forefinger  and  thumb  of  one  hand  must  be  kept  constantly  on  the 
milled-head  of  the  fine  focussing  screw.  Supposing  the  light  to  be 
on  our  right,  we  devote  the  right  hand  to  the  focussing. 

The  left  hand  will  be  engaged  with  the  glass  slip  upon  which  the 
object  has  been  mounted.  The  forearm  resting  upon  the  table,  let 
the  thumb  and  forefinger  rest  on  the  left  upper  side  of  the  stage,  just 


MAGNIFYING    POWER  AND   MEASUREMENT    OF    OBJECTS.  7 

touching  the  edges  of  the  glass  slip.  The  slightest  pressure  will  then 
enable  you  to  move  the  slip  smoothly,  steadily,  and  delicately. 

Proceed'  to  examine  the  object  with  method.  Suppose  a  section 
of  some  tissue  to  be  under  examination — say  one-fourth  of  an  inch 
square.  With  the  high  power  you  will  be  able  to  see  only  a  small 
fraction  of  the  area  at  once.  Commence  at  one  corner  to  observe  ; 
and  with  the  left  hand  move  the  object  slowly  in  successive  parallel 
lines,  preserving  the  focus  with  the  right  hand,  until  the  whole  area 
of  the  section  has  been  traversed. 

Practice  will  soon  establish  perfect  co-ordination  of  the  movements 
involved,  and  will  result  in  the  ability  to  work  with  ease,  celerity, 
and  profit. 

CONSERVATION    OF   THE   EYESIGHT. 

I 

The  beginner  should  not  become  accustomed  to  the  use  of  one  eye 
alone,  or  of  closing  either,  in  microscopical  work.  It  will  require  but 
little  practice  to  use  the  eyes  alternately,  and  the  retinal  image  of  the 
unemployed  eye  will  soon  be  ignored  and  unnoticed. 

MAGNIFYING   POWER   AND   MEASUREMENT   OF   OBJECTS. 

The  microscope  is  not,  as  the  beginner  usually  supposes,  to  be 
valued  according  to  its  power  of  magnification,  but  rather  according 
to  the  clearness  and  sharpness  of  the  image  afforded. 

Magnifying  power  is  generally  expressed  in  diameters.  A  certain 
area  is  by  the  instrument  made  to  appear,  say,  ten  times  as  large  as  it 
appears  to  the  naked  eye.  This  object  has,  then,  its  apparent  area 
increased  one  hundred  times ;  but  reference  is  made  in  describing 
such  phenomena  only  to  amplification  in  a  single  direction.  The  dia- 
meter has  been  increased  ten  times  and  would  be  expressed  by  pre- 
fixing the  sign  of  multiplication,  e.  g.,  X  10. 

A  convenient  unit  of  approximate  measurement  for  the  histologist 
is  the  apparent  size  of  a  human  red  blood-corpuscle  with  a  given  objec- 
tive. Thirty-two  hundred  corpuscles,  placed  side  by  side,  would 
measure  one  inch  ;  or,  we  say,  the  diameter  of  a  single  corpuscle  is 
the  thirty-two  hundredth  of  an  inch.  After  considerable  practice,  you 
will  become  accustomed  to  the  apparent  size  of  this  object  with  a  cer- 
tain objective  and  eye-piece.  This  will  aid  in  an  approximate  mea- 
surement of  objects  by  comparison,  and  will  further  give  the  magni- 
fying power  of  the  microscope.  If  a  corpuscle  appears  magnified  to 
one  inch  in  diameter,  it  is  evident  that  the  instrument  magnifies 
thirty-two  hundred  times.  Should  the  diameter  appear  one-quarter 
of  an  inch,  the  power  is  eight  hundred;  one-eighth  of  an  inch,  four  hun- 


8  PRACTICAL    MICBOSCOPY. 

dred,  etc.  The  instrument  which  I  have  heretofore  described,  with  the 
high  power  in  use  and  the  tube  withdrawn,  will  present  the  corpuscle 
as  averaging  very  nearly  one-eighth  of  an  inch  in  diameter —  x  400. 
Whil  ethis  gives  a  gross  idea  of  amplification,  the  method  will  often 
prove  inaccurate  because  of  individual  errors  in  the  estimation  of 
proportions. 

Use  of  the  Stage- Micrometer. — From  a  dealer^in  optical  goods  pur- 
chase a  Rogers''  *  glass  stage-micrometer,  ruled  in  hundredths,  thou- 
santdhs,  and  five-thousandths  of  an  inch.  Also  procure  from  the 
dealer  in  drawing  instruments  a  two-inch  boxwood  rule  divided  deci- 
mally to  fiftieths. 

Place  the  micrometer  on  the  stage  of  the  microscope  and  focus  the 
lines.  Then  place  the  rule  also  on  the  stage,  but  Justin  front  of  and 
parallel  with  the  micrometer.  By  a  little  practice,  using  both  eyes, 
the  two  rulings  may  be  seen  simultaneously,  and  by  adjusting  the 
position  of  the  rule,  the  lines  may  be  made  to  appear  superposed. 

Let  us  suppose  that,  with  a  given  eye-piece  and  objective,  the 
thousandth  divisions  on  the  micrometer  correspond  exactly  with  one 
of  the  tenths  of  the  rule.  Keeping  this  in  mind,  remove  the  micro- 
meter scale  and  substitute  an  object,  say  a  blood  slide.  Let  us  again 
suppose  that  the  image  of  a  given  red  corpuscle  appears  to  cover 
three  of  the  one-tenth  inch  rulings,  the  latter  scale  having  been  left 
in  position.  It  is  evident  that,  as  we  found  the  value  of  one  of  the 
rule  tenths  to  be,  by  the  micrometer,  the  one-thousandth  of  an  inch, 
the  globule  measures  one  three-thousandth  of  an  inch  in  diameter. 

The  value  of  the  rule  divisions  must  be  determined  for  each  objec- 
tive ;  and  a  memorandum  will  then  provide  the  means  of  quickly  ob- 
taining a  very  close  approximation  of  the  size  of  objects  as  viewed  in 
the  microscope,  and  at  the  same  time  indicate  the  degree  of  ampli- 
fication of  the  instrument  itself. 

SKETCHING   FROM  THE   MICEOSCOPE. 

Let  me  most  emphatically  urge  the  practice  of  sketching  in  con- 
nection with  microscopy.  "  I  am  no  artist,"  or  "  I  have  no  skill  in 
drawing,"  is  often  the  reply  to  my  advice  in  this  matter.  I  then  sug- 
gest that  no  special  skill  is  needed  to  begin  with,  only  patience  and  a 
dogged  determination  to  succeed.  The  pictures  in  the  microscopic 
field  have  no  perspective,  and  may  be  reproduced  in  outline  merely. 

*  The  micrometer  rulings  of  Professor  Rogers,  of  Cambridge  University, 
are  without  doubt  of  surpassing  excellence.  They  are  the  result  of  many 
years  of  unwearying  experimentation  and  are  recognized  standards  through- 
out the  scientific  world. 


SECTION    CUTTING. 

Begin  with  simple  tissues,  reserving  intricate  detail  until  a  short 
period  of  practice  gives  the  technique  needed.  I  do  not  recommend 
the  camera  lucida,  as  my  experience  strongly  impresses  me  with  this 
as  a  fact,  that  he  who  cannot  sketch  without  a  camera  will  never 
sketch  with  one.  Pencil  drawings  may  be  very  effectively  colored 
with  our  staining  fluids,  diluted  if  necessary. 

PREPARATIONS     OF    TISSUES    EOR    MICROSCOPICAL 

PURPOSES. 

TISSUES   ARE    STUDIED   BY   TRANSMITTED    LIGHT. 

The  microscopical  study  of  both  normal  and  pathological  tissues  is 
invariably  conducted  by  the  aid  of  transmitted  light. 

Tissues,  if  not  naturally  of  sufficient  delicacy  to  transmit  light, 
must  in  some  way  be  made  translucent. 

Delicate  tissues  like  omenta,  desquamating  epithelia,  fluids  con- 
taining morphological  elements,  certain  fibres,  etc.,  are  sufficiently 
diaphanous,  and  require  no  preparation.  Such  objects  are  simply 
placed  upon  the  glass  slip,  a  drop  of  som'e  liquid  added,  and,  when 
protected  by  a  thin  covering  glass,  are  ready  for  the  stage  of  the 
microscope. 

PREPARATION   BY   TEASING. 

The  elements  of  structures  mainly  fibrous,  e.  g.,  muscle,  nerve, 
ligament,  etc.,  are  well  studied  after  a  process  of  separation,  by 
means  of  needles,  known  as  teasing.  A  minute  fragment  of  the  organ 
or  part  having  been  isolated  by  the  knife  or  scissors  is  placed  upon  a 
glass  slip,  and  a  drop  of  some  fluid  which  will  not  alter  the  tissue 
added.  Stout  sewing  needles,  stuck  in  slender  wood  handles,  are 
commonly  employed  in  the  teasing  process.  The  separation  of  tissues 
is  frequently  facilitated  by  means  of  dissociating  fluids  which  remove 
the  cement  substance.  fi 

SECTION    CUTTING. 

After  having  become  familiar  with  the  various  elementary  struc- 
tures of  animal  tissues,  we  proceed  to  the  study  of  their  relation  to 
organs. 

As  the  teasing  process  is  not  available  with  such  complicated 
structures  as  lung,  liver,  kidney,  brain,  etc.,  we  resort  to  methods  of 
slicing,  i.  e.,  section  cutting. 

Sections  must  be  made  of  extreme  tenuity,  in  order  that  the  natu- 


10  PRACTICAL   MICROSCOPY. 

rally  opaque  structures  may  be  illuminated  by  transmitted  light. 
This  becomes  an  easy  matter  with  such  tissues  as  cartilage;  but  some, 
like  bone,  are  much  too  hard  to  admit  of  cutting,  and  others  are  as 
much  too  soft;  so  that  while  certain  tissues  must  be  softened,  the 
majority  must  be  hardened.  Fortunately,  both  of  these  conditions 
may  be  secured  without  in  any  way  altering  the  appearance  or  rela- 
tions of  the  structures.  Hardening  processes,  from  necessity,  become 
a  prominent  feature  in  histological  work;  but  I  propose  here  to  indi- 
cate some  of  the  more  useful  methods  of  section-cutting,  reserving 
the  hardening  processes  for  another  place. 

FREE-HAND   SECTION  CUTTING. 

My  students,  when  ready  for  this  work,  are  provided  with  some 
tissue  which  has  been  previously  hardened.  We  will  take,  for  ex- 
ample, a  piece  of  liver  which  has  been  rendered  sufficiently  firm  for 
our  work  by  immersion  in  alcohol,  and  proceed  to  direct  the  steps  in 
obtaining  suitable  sections  by  the  simple  free-hand  method. 


FIG.  3.— FREE-HAND  SECTION  CUTTING. 

I  wish  to  strongly  emphasize  the  importance  of  this  mode  of  cut- 
ting. A  moderate  amount  of  practice  will  render  the  microscopist 
independent  of  all  appliances,  save  those  of  the  most  simple  character 
and  which  are  always  obtainable. 

An  ordinary  razor,  with  keen  edge,  and  a  shallow  dish,  preferably 
a  saucer,  partly  filled  with  alcohol  are  required.  The  razor  best 


FKEE-HAND    SECTION   CUTTING.  ll 

adapted  to  the  work  is  concave  on  one  side  (the  upper  side  as  seen 
in  Fig.  3)  and  nearly  flat  on  the  other,  although  this  is  largely  a  mat- 
ter of  personal  preference. 

Fig.  3  indicates  the  proper  position  of  the  hands  in  commencing 
the  cut.  I  have  made  the  sketch  from  a  photograph  of  my  esteemed 
colleague,  Dr.  Wesley  M.  Carpenter.  The  student  should  be  seated 
at  a  table  of  such  height  as  to  afford  a  convenient  rest  for  the 
forearms.  A  small  piece  of  tissue  is  held  between  the  thumb  and 
forefinger  of  the  left  hand,  so  that  it  projects  slightly  above  both. 
(In  the  cut,  a  cube  of  tissue,  too  small  to  handle  in  this  way,  has  been 
cemented  to  a  cork  with  paraffin  in  the  manner  hereafter  described, 
and  the  cork  held  as  just  mentioned.)  The  hand  carrying  the  tissue 
is  held  over  the  saucer  of  alcohol.  The  razor,  held  lightly  in  the 
right  hand,  as  seen  in  the  figure,  is,  previous  to  making  every  cut, 
dipped  flatwise  into  the  alcohol,  so  as  to  wet  it  thoroughly;  and  is 
then  lifted  horizontally,  carrying  several  drops,  perhaps  half  a  drachm 
of  the  fluid  on  the  concave,  upper  surface.  The  alcohol  serves  to 
prevent  the  section  from  adhering  to  the  knife,  and  to  moisten  the 
tissue.  If  allowed  to  become  dry,  the  latter  would  be  ruined  by 
alterations  of  structure. 

Now  as  to  the  manner  of  moving  the  knife.  Resting  the  under 
surface  upon  the  forefinger  for  steadiness,  bring  the  edge  of  the  blade 
nearest  the  heel  to  the  margin  of  the  tissue  furthest  from  you. 
Then,  entering  the  edge  just  below  the  upper  surface  of  the  tissue, 
with  a  light  but  steady  hold  draw  the  knife  toward  the  right,  at  the 
same  time  advancing  the  edge  toward  the  body.  This  passes  the 
knife  through  the  tissue  diagonally,  and  leaves  the  upper  surface  of 
the  latter  perfectly  flat  or  level.  Remove  the  piece  which  has  been 
cut  and  repeat  the  operation.  Do  not  attempt  to  cut  large  or  very 
thin  sections  at  first.  A  minute  fragment,  if  thin,  is  valuable. 

As  the  razor  is  drawn  through  the  tissue,  the  section  floats  in  the 
alcohol;  depress  the  point  of  the  knife  and  the  section  will  slide  into 
the  saucer  of  spirit,  and  thus  prevent  its  injury.  If  it  does  not  leave 
the  knife  readily,  brush  it  along  with  a  camel's  hair  pencil  which  has 
been  well  wetted  with  the  alcohol. 

Proceed  in  the  above  manner  until  the  tissue  is  exhausted,  when 
you  will  have  a  great  number  of  sections,  large  and  small,  thick  and 
thin.  Selecting  the  thinnest,  lift  them  c  tref ully  with  a  needle,  one 
at  a  time,  into  a  small,  wide-mouthed  bottle  of  alcohol ;  cork  and 
label  for  future  use. 

When  the  work  is  finished,  and  before  the  spirit  has  evaporated 
from  your  fingers— it  is  impossible  to  avoid  wetting  the  skin  more  or 


12  PRACTICAL     MICROSCOPY. 

less — wash  them  thoroughly,  and  wipe  dry.  This  saves  the  roughen- 
ing of  the  hands  which  is  apt  to  result  when  alcohol  has  been  allowed 
to  dry  upon  them  repeatedly. 


SECTION-CUTTING   WITH   THE   STIRLING    MICROTOME. 

Of  the  numerous  mechanical  aids  to  section-cutting,  I  shall  men- 
tion only  two  or  three.  One  of  the  earlier  and  better  known  instru- 
ments is  seen  in  Fig.  4.  The  Stirling  microtome  consists  essentially 
of  a  short  brass  tube,  into  which  the  tissue  is  fixed,  either  by  pressure 


FIG.  4.— STIRLING'S  MICROTOME. 

or  by  imbedding  in  wax.  A  screw  enters  below  which,  acting  on  a 
plug,  raises  the  contents  of  the  tube.  As  the  material  to  be  cut  is 
raised  from  time  to  time  by  the  screw,  it  appears  above  the  plate 
which  surrounds  the  top  of  the  tube.  This  plate  steadies  and  guides 
the  razor ;  and  it  is  evident  that  more  uniform  sections  may  be  cut 
with  this  little  apparatus  than  would  be  possible  with  nothing  to  sup- 
port the  knife,  or  to  regulate  thickness,  beyond  the  unaided  skill  of 
the  operator. 

Much  depends  upon  the  manner  in  which  the  material  is  fixed  in 
the  tube  or  well  of  the  microtome.  If  the  tissue  be  of  a  solid 
character,  like  liver,  kidney,  spleen,  many  tumors,  etc.,  it  may  be 


SECTION    CUTTING   WITH   THE    STIRLING   MICROTOME. 


13 


surrounded  with  some  carefully  fitted  pieces  of  elder-pith,*  carrot, 
etc.,  and  the  whole  pressed  evenly  and  quite  firmly  into  the  well.  A 
small  piece  of  tissue  which,  by  cutting,  can  be  made  somewhat  cubical 
in  shape,  may  be  surrounded  by  slabs  of  pith,  carrot,  or  turnip,  shaped 
as  in  Fig.  5.  Indeed,  the  fragments  of  imbedding  material  can  be 
shaped  so  as  to  fit  tissue  of  almost  any  form.  Before  the  whole  is 
pressed  into  the  well  of  the  microtome,  the  bottom,  against  which 
the  brass  plug  fits,  should  be  cut  off  square. 

The  wax  method  of  imbedding  is  employed  with  tissues  such  as 
brain,  lung,  soft  tumors,  etc.,  which  might  be  injured  by  the  previous 
treatment.  To  three  parts  of  paraffin  wax  (a  paraffin  candle  answers 
perfectly)  add  one  part  of  vaseline,  and  heat  until  thoroughly  mixed. 
The  microtome  having  been  previously  warmed — standing  upright, 
is  filled  with  the  imbedding  mixture.  The  piece  of  tissue  is  then 


FIG.  5.— MANNER  OF  CUTTING  AND  ARRANGING  PIECES  OP  PITH,  TURNIP,  ETC.,  FOR  SUPPORTING 
HARDENED  TISSUE  IN  THE  WELL  OF  A  MICROTOME. 

carefully  wiped  dry  with  the  blotting  paper  and,  just  as  the  imbedding 
begins  to  congeal  around  the  edges,  is  pressed  below  the  surface  with 
a  needle  and  held  until  the  cool  mixture  fixes  it  in  position.  The 
whole  is  now  allowed  to  become  thoroughly  cold.  By  turning  the 
screw,  the  plug  of  wax  is  raised  ;  and  it  must  be  gradually  cut  away, 
by  sliding  the  knife  across  the  plate,  until  the  upper  part  of  the 
tissue  appears. 

Before  commencing  to  cut  sections — however  the  tissue  may  have 
been  imbedded — provide  yourself  with  a  saucer  of  alcohol  and  a 
camel's-hair  pencil.  Having  wetted  the  knife,  turn  the  screw  so  that 
the  tissue,  with  its  imbedding,  appears  slightly  above  the  plate  of  the 
microtome  ;  and  then,  resting  the  blade  of  the  razor  on  the  plate 

*The  pith  from  the  young  shoots  of  Ailantus  glandulosus  (improperly  called 
"  Alanthus  "),  gathered  in  early  autumn,  is  the  best  material  for  this  method 
of  imbedding  with  which  I  am  acquainted.  The  wood  is  easily  cut  from  the 
pith,  and  the  latter  is  very  large  and  firm. 


PRACTICAL     MICROSCOPF. 


(vide  Fig.  6),  make  the  cut  precisely  as  in  free-hand  cutting.  The- 
section  is  then  brushed  off  into  the  saucer,  the  screw  turned  up 
slightly,  the  razor  wetted,  and  a  second  cut  made.  These  steps  are 
repeated  until  the  required  number  of  sections  has  been  obtained. 


FIG.  6.— METHOD  OP  CUTTING  SECTIONS  WITH  THE  STIRLING  MICROTOME. 

The  imbedding  will  leave  the  cuts  as  they  are  floated  in  the  alcohoL 
They  may  now  be  selected,  lifted  with  the  needle  into  clean  spirit^ 
and  preserved  as  before  indicated,  for  future  operations. 


THE   SCHRAUEE   MICROTOME. 

Fig.  7  represents  an  improvement  on  the  Stirling  instrument,  and 
a  most  convenient,  practical  and  inexpensive  microtome  for  the  phy- 
sician. 


FIG.  7.— SCHRAUER'S  IMPROVED  STIRLING  MICROTOME, 
With  clamp  for  holding  the  tissue. 

The  tissue,  if  sufficiently  hard,  is  held  in  a  clamp  or  vice  in  the 
well  of  the  instrument,  the  pressure  being  regulated  by  the  side 
screw.  By  this  means  the  necessity  of  imbedding  is  avoided.  If  the 


THE    AUTHOR  S    LABORATORY  MICROTOME. 


15 


tissue  be  too  soft  to  withstand  such  treatment,  it  is  best  cemented  to 
a  cork,  and  the  cork  then  fastened  in  the  clamp.  A  screw-thread  is 
cut  upon  a  short  cylinder,  which  works  in  a  corresponding  thread 
chased  on  the  inside  of  the  well-tube.  The  short  cylinder  carries  the 
knife-plate,  and,  as  the  latter  is  turned  to  the  right,  the  whole  de- 
scends and  the  tissue  projects,  ready  to  be  sliced  off. 

THE  AUTHOR'S  LABORATORY  MICROTOME. 

For  certain  work,  some  form  of  microtome  becomes  necessary  in 
which  the  operator  is  relieved  from  supporting  the  knife.  Fig.  8  is  a 
sketch  from  such  an  instrument  which  I  have  contrived  and  which 
has  been  in  daily  use  in  my  laboratory  for  over  three  years. 

The  carriage  A,  supporting  the  knife  B,  is  of  solid  cast-iron  ;  and 
has,  upon  the  under  side,  a  V  guide,  which  fits  into  the  longitudinal 
groove  0  of  the  base  D.  Parallel  with  this  groove  is  a  smooth  flat 


FIG.  8.— THE  AUTHOR'S  LABORATORY  MICROTOME. 

The  instrument  consists  of  a  very  heavy  cast-iron  bed  upon  which  a  carriage  supporting  a 
knife  is  made  to  slide.  The  tissue  is  cemented  with  paraffin  (or  held  in  an  adjustable  clamp 
not  shown  in  the  cut)  to  a  table,  which  can  be  raised  by  a  fine  steel  screw.  The  thickness  of  the 
section  to  be  cut  is  controlled  by  turning  the  milled  head  actuating  the  finely  threaded  screw. 

surface,  upon  which  also  travels  the  rib  E  of  the  knife-carriage.  A 
second  Y  has  been  avoided,  in  order  to  diminish  friction.  The  knife 
is  clamped  rigidly  to  the  upper  surface  of  the  carriage,  by  means  of  a 
Willis'  tool-holder,  consisting  of  a  steel  plate  F,  a  nut  G-,  and  washer 
H. 

The  mechanism  for  supporting  and  positioning  the  tissue — not  shown 
in  the  sketch— is  built  upon  a  plate  I,  which  can  be  quickly  fixed  to 
the  body  of  the  microtome  at  the  height  and  lateral  incline  required 
by  the  large  set-screws  J,  J'.  The  mechanism  for  raising  the  tissue 
to  the  knife,  between  the  cuts,  consists  of  a  screw  K,  of  fifty  threads 
to  the  inch  which,  working  in  the  nut  L,  elevates  the  bevelled  slide 


16  PRACTICAL     MICROSCOPY. 

M,  to  which  the  tissue  N  is  affixed.  An  ether-freezing  attachment 
may  be  substituted  for  the  plate  I. 

The  milled-head  0  is  divided  into  one  hundred  parts,  so  that  each 
fraction  of  a  turn  raises  the  tissue  -g- oW  °f  an  inch. 

The  knife  should  possess  an  edge  of  the  most  exquisite  keenness ; 
and  this  holder  admits  the  employment  of  almost  any  cutting  instru- 
ment. In  order  to  the  production  of  the  best  results,  the  knife 
should  be  set  at  the  most  acute  angle  compatible  with  the  use  of  the 
•entire  length  of  the  cutting  edge,  from  heel  to  point.  Both  knife 
and  tissue  are  to  be  flooded  with  alcohol,  in  ordinary  work,  as  in  free- 
hand cutting.  A  drip  pan  is  provided,  and  is  placed  below  the  tissue- 
carrier.  A  groove  in  the  front  upper  edge  of  the  base  prevents  the 
pirit  from  flowing  over  the  track,  which.,  mixing  with  the  lubricating 
oil  covering  the  latter,  would  interfere  with  the  delicacy  and  ease  of 
the  sliding  motion. 

The  value  of  this  instrument  is  largely  consequent  upon  its  great 
solidity — the  base  weighing  from  eighteen  to  twenty-five  pounds,  with 
the  knife  carriage  correspondingly  heavy.  Just  why  such  weight 
and  solidity  are  necessar}7,  and  contribute  so  largely  to  our  success  in 
cutting  sections,  is  not  at  once  apparent.  The  microtome  is  now 
made  by  Mr.  L.  Schrauer,  of  New  York,  in  two  sizes  ;  the  smaller 
carrying  a  knife  fourteen,  and  the  larger,  eighteen  inches.  A  smaller 
pattern  would  present  no  special  advantages  over  microtomes  already 
in  use. 

SHARPENING   KNIVES. 

In  the  majority  of  instances  of  failure  to  produce  suitable  sections 
for  microscopical  work,  the  cause  can  be  set  down  to  dull  knives;  and 
I  would  urge  the  student  to  practice  honing,  until  able  to  put  cutting 
instruments  in  good  condition.  If  he  will  but  start  properly,  success 
is  sure.  Nine-tenths  of  the  microtomes  are  purchased  because  of 
failure  in  free-hand  work  with  a  dull  knife;  but  no  advantage  will  be 
gained  by  a  machine,  if  1  he  student  be  incapable  of  keeping  the  knife 
up  to  a  proper  degree  of  keen  ness. 

A  knife  is  a  wedge,  and  for  our  purposes  the  edge  must  be  of  more 
than  microscopical  tenuity — it  being  impossible,  with  the  microscope, 
to  discover  notches  and  nicks  if  properly  sharpened. 

It  is  impossible  to  secure  the  best  results  with  indifferent  tools. 
The  knife  should  be  hard  enough  to  support  an  edge,  but  not  so  hard 
as  to  be  brittle.  The  proper  temper  is  about  that  given  a  good  razor. 

We  need  at  least  two  hones — one  comparatively  coarse,  for 
removing  slight  nicks;  and  another,  for  finishing.  The  first  part  of 
the  work  is  best  done  by  means  of  a  sort  of  artificial  hone  made  with 


SHARPENING    KNIVES.  17 

ground  corundum.  These  are  kept  in  stock  by  dealers  in  mechanics' 
supplies  of  great  variety  in  size  and  fineness.  For  razors  a  "00" 
corundum  slip  will  best  answer.  This  will  very  rapidly  remove  the 
inequalities  from  an  exceedingly  dull  razor.  A  Turkish  hone  will  be 
best  for  finishing.  For  my  large  knives  I  use  a  third,  very  soft  and 
fine  stone,  known  as  water-of-Ayr. 

Let  the  corundum  slip  be  placed  on  a  level  support  (mine  are  fitted 
into  blocks  like  the  carpenter's  oil-stone),  and  cover  the  surface  liber- 
ally with  water.*  The  hones  should  always  be  worked  wet.  Place  the 
knife  flat  on  the  stone  near  the  right  hand  as  at  A,  Fig.  9.  Draw 
steadily  in  the  direction  of  the  curved  dotted  line,  i.  e.,  from  right 
to  left — holding  the  blade  firmly  on  the  stone  B  with  slight  pressure 


FIG.  9. 


FIG.  10. 

FIGS.  9  AND  10. — METHOD  OF  HONING. 

The  knife  is  first  brought  with  its  heel  in  the  position  shown  at  A,  Fig.  9.  It  is  then  drawn 
forward  as  indicated  by  the  curved  dotted  line  until,  at  the  end  of  the  stroke,  the  position  C  is 
attained.  Fig.  10  indicates  the  method  of  turning  the  blade  before  reversing  and  between 
each  stroke. 


until  the  position  C  is  attained.  Eotate  the  razor  on  its  back — vide 
Fig.  10 — so  as  to  bring  the  other  side  on  the  stone;  and  draw  from 
left  to  right.  Observe  that  as  the  knife  is  drawn  from  side  to 
side  (the  edge  invariably  looking  to  ward  the  draw)  it  is  always  worked 
from  heel  to  point.  The  amount  of  pressure  may  be  proportioned  to 
the  condition  of  the  edge.  If  it  be  badly  nicked,  considerable  pres- 
sure may  be  employed;  while,  as  it  approaches  keenness,  the  pressure 

*  A  few  drops  of  glycerin  added  to  the  water  retards  evaporation  and 
appears  to  keep  the  surface  of  the  hone  in  good  condition. 


18  PRACTICAL     MICROSCOPY. 

is  to  be  lessened,  until  the  weight  of  the  blade  alone  gives  sufficient 
friction. 

Kepeat  the  process  fifteen  or  twenty  times,  and  examine  the  blade. 
If  the  nicks  are  yet  visible,  continue  honing  until  they  can  no  longer 
be  seen.  Then  draw  the  edge  across  the  thumb  nail.  Do  this  lightly 
and  the  sense  of  touch  will  reveal  indentations  which  the  eye 
failed  to  recognize.  Continue  the  use  of  the  coarse  stone  until  the 
edge  is  perfect,  as  far  as  the  thumb-nail  test  indicates. 

The  knife  is  then  to  be  carefully  wiped,  so  as  to  remove  any  coarse 
particles  of  corundum,  and  applied  to  the  wetted  Turkish  hone  with 
precisely  the  same  motions  as  were  employed  in  the  first  process.  Af- 
ter a  dozen  or  two  strokes,  examine  the  edge,  by  applying  the  palmar 
aspect  of  the  thumb,  with  repeated  light  touches,  from  heel  to  point. 
This  looks  slightly  dangerous  to  the  novice,  but  it  is  an  excellent 
method  of  determining  the  condition.  Of  course  actual  trial  with  a 
piece  of  hardened  tissue  is  the  best  test. 

Some  most  skilful  technologists  prefer  to  finish  by  stropping.  I 
have  not  used  a  strop  in  my  laboratory  for  over  two  years,  preferring 
to  use  the  knife  as  it  comes,  highly  finished,  from  the  water-of-Ayr 
hone.  If  a  strop  be  employed,  the  leather  should  be  glued  smoothly 
to  a  support  of  wood,  otherwise  the  edge  of  the  knife  will  become 
rounded. 

Stropping  is  conducted  in  the  same  manner  as  honing,  only  the  edge 
of  the  knife  follows  the  stroke  instead  of  leading  it. 

SUPPORTING  TISSUES   FOR   CUTTING. 

Frequently  small  bits  of  tissue  are  required  to  be  cut — pieces  too 
small  to  be  held  with  the  fingers.  I  am  in  the  habit  of  cementing 
such  tissues  into  a  hole  in  a  bit  of  ailantus  or  elder  pith,  when  the 


FIG.  11.— INSTRUMENT  FOR  SOLDERING  TISSUE  TO  CORK  SUPPORTS  WITH  PARAFFIN. 

It  consists  of  an  awl  handle  of  wood  into  which  a  short  piece  of  wire,  preferably  copper,  is 
driven  and  bent  as  shown. 


whole    may   be   cut   as   one   mass.     Tissue  is   frequently    cemented 
to  cork  for  convenience  of  holding  in   free-hand  cutting;  or  the  cork 


SUPPORTING    TISSUES   FOE    CUTTING.  19 

may  be   held  in   the  vise  of  the  microtome.     The  edge  of  the  knife 
should  not  be  allowed  to  touch  the  cork. 

Fig.  11  shows  a  simple  little  instrument,  very  convenient  for  using 
paraffin  as  a  cement.  A  piece  of  stout  copper  or  brass  wire  is  bent 
as  indicated,  pointed,  and  driven  into  an  ordinary  awl  handle. 
Paraffin  wax  possesses  the  very  valuable  property  of  remaining  solid 
at  ordinary  temperatures,  not  cracking  in  the  cold  of  winter  or 
softening  in  summer.  It  is  unaltered  by  most  reagents,  is  easily 
rendered  fluid,  and  quickly  solidifies.  As  a  cement,  it  is  invaluable 
to  the  microscopical  technologist. 


FIG.  12.— MODE  OF  CEMENTING  TISSUE  TO  A  CORK  SUPPORT  WITH  PARAFFIN. 

Fig.  12  indicates  the  method  of  cementing  a  piece  of  tissue  to  a 
cork  or  other  support.  The  tissue  having  been  properly  placed,  the 
wire  tool  is  heated  for  a  moment  in  the  alcohol  flame,  and  then 
touched  to  a  cake  of  paraffin.  The  paraffin  is  melted  in  the  vicinity 
of  the  hot  wire,  a  drop  adheres  to  the  latter  and  is  carried  to  the  edge 
of  the  tissue.  In  the  cut  the  wire  tool  is  seen  in  the  position  neces- 
sary for  cementing  one  edge.  The  wire  being  removed,  the  wax  im- 
mediately cools  and  becomes  solid.  The  other  sides  are  afterward 
cemented  in  like  manner.  The  whole  is  done  in  less  time  than  is 
necessary  to  the  description  of  the  process. 


20  PRACTICAL    MICROSCOPY. 


PREPARATION"   OF   TISSUES   FOR   CUTTING,    ETC. 

We  have  already  seen  that  most  animal  tissues  are  unsuitable  for 
the  production  of  thin  sections  until  hardened. 

It  is  also  a  fact,  paradoxical  though  it  may  seem,  that  fresh  tissues 
do  not  present  truthful  appearances  of  structural  elements.  The  old- 
school  histologists  insisted  upon  the  presentation  of  structures  unal- 
tered by  chemical  substances,  while  the  modern  worker  has  discarded 
such  tissue  with  very  few  exceptions.  Many  descriptions  of  structure 
and  growth,  the  result  of  study  upon  fresh  material,  have  been  proven 
by  later  methods  grossly  inaccurate. 

It  is  impossible  to  remove  tissues  from  the  living  animal  and  to  sub- 
ject them  to  microscopical  observation  without,  at  the  same  time,  ex- 
posing them  to  such  radical  changes  of  environment  as  to  produce 
structural  alterations.  Certain  tissues,  presenting  in  the  living  con- 
dition stellate  cells  with  the  most  delicate,  though  well-defined 
branching  processes,  when  removed  from  contact  with  the  body,  how- 
ever expeditiously,  afford  no  hint  of  anything  resembling  such  ele- 
ments, as  they  are  quickly  reduced  to  simple  spherical  outlines. 

In  short,  it  is  impossible  to  study  fresh  material,  as  such,  without 
constant  danger  of  erroneous  conclusions,  as  retrograde  alterations  of 
structure  commence  with  surprising  rapidity  the  moment  a  part  is 
severed  from  the  influences  which  control  the  complete  organism. 

From  what  has  been  said  we  appreciate  the  necessity  of  agents 
which,  when  applied  to  portions  freshly  removed  from  the  animal,  or 
even  before  removal,  shall  instantly  stop  all  physiological  processes 
and  retain  the  elements  in  permanent  fixity. 

Very  much  of  the  human  structure  which  is  available  will  be  se- 
cured only  after  functional  activities  have  long  ceased,  and  the  structure 
essentially  altered.  We  are,  therefore,  compelled  to  resort  to  the  use 
of  material  from  the  lower  animals  in  very  many  instances. 

ALCOHOL   HARDENING. 

The  tissue,  whatever  process  may  be  in  contemplation,  having  been 
removed  from  the  body  as  quickly  after  death  as  possible,  ivithout 
washing  or  allowing  contact  with  water  in  any  way,  should,  with  a 
sharp  scalpel,  be  divided  into  small  pieces.  Of  the  more  solid  organs, 
pieces  one-half  inch  square  by  one-fourth  inch  thick  will  be  suf- 
ficiently small,  and  they  will  harden  rapidly.  The  smaller  the  pieces 
and  the  larger  the  quantity  of  hardening  fluid  the  more  quickly  will 
the  process  be  completed.  The  volume  of  fluid  should  exceed  that  of 


CHROMIC    ACID    FIXING    AND    HARDENING.  21 

the  tissue  at  least  twenty  times.  Wide  mouth,  well-stoppered  bottles, 
from  one  ounce  to  a  pint,  or  even  larger,  are  best ;  and  they  should 
be  carefully  labelled  and  kept  in  a  cool  place  with  occasional  agita- 
tion. 

Quick  Method. — A  piece  of  any  solid  organ,  say  liver,  spleen,  pan- 
creas, kidney,  uterus,  lymph-node,  etc.,  not  larger  than  one  half 
inch  square  by  one-eighth  thick,  may  be  perfectly  hardened  in  twelve 
hours  by  immersion  in  one  ounce  of  ninety  five  percent,  alcohol.  No 
more  should  be  thus  prepared  than  is  to  be  cut  within  twenty-four 
hours,  on  account  of  the  shrinkage  which  results  after  the  prolonged 
immersion  of  solid  structures  in  strong  spirit. 

After  the  tissue  has  been  one  hour  in  the  above,  it  maybe  hardened 
in  one  or  two  hours  more,  if  transferred  to  absolute  alcohol.  This 
method  is  of  frequent  advantage  in  pathological  histology. 

Ordinary  Method. — The  method  quite  general  here,  and  intended 
to  prevent  shrinkage,  is  as  follows  : 

The  organs,  cut  into  pieces  from  one-half  to  three-fourths  of  an  inch 
cube,  are  placed  in  a  mixture  of  alcohol  one  part,  water  two  parts 
(called  in  this  laboratory  "  Alcohol  A")  for  twelve  hours.  This  re- 
moves the  blood,  and  prepares  the  tissue  for  the  next  mixture — alco- 
hol one  part,  water  one  part,  ("Alcohol  B  ")  where  it  remains  twenty- 
four  hours.  The  pieces  are  afterward  removed  to  ninety-five  per- 
cent alcohol  ("Alcohol  C").  The  strong  alcohol  completes  the  hard- 
ening, and  serves  as  a  preservative  until  such  time  as  sections  may  be 
required.  The  process  is  complete  in  from  two  to  four  weeks,  and 
the  material  will  keep  without  deterioration  for  three  or  four  years, 
especially  if  the  spirit  be  changed  occasionally. 

Ordinary  anatomical  specimens  which  have  been  preserved  in  dilute 
alcohol  are  of  no  value  for  our  purpose. 

CHROMIC    ACID   FIXING    AND    HARDENING. 

Chromic  acid  is  a  very  deliquescant  salt,  and  is  best  preserved  by 
making  a  strong  solution  at  once,  and  then  diluting  it  as  may  be 
needed.  A  stock  solution  may  be  made  as  follows  : 

Chromic  acid  (crystals),     .  .         .         .       25  grammes. 
Water  (distilled  or  rain),         .         .    .      .75  cubic  cent.      M. 

For  general  use,  dilute  20  parts  with  600  parts  of  water,  which  gives 
a  strength  of  nearly  one-sixth  of  one  per  cent. 

The  tissue,  as  soon  as  secured  and  properly  divided,  is  placed  in  the 
above,  remembering  the  rule  regarding  quantity.  Change  in  twenty- 
four  hours  to  fresh  solution,  and  again  on  the  third  day.  In  seven 
days,  or  thereabout,  change  the  fluid  again.  The  tissue  must  now  be 


22  PRACTICAL     MICROSCOPY/. 

watched  carefully  and  when,  on  cutting  through  a  piece,  the  fluid  is 
found  to  have  stained  the  blocks  completely,  taking  from  two  to 
three,  or  even  four  weeks,  remove  to  a  large  jar  of  clear  water  and 
wash,  changing  the  water  frequently  for  twenty-four  hours.  The 
washing  having  removed  the  chromic  acid,  the  tissue  is  further  hard- 
ened in  Alcohol  A,  B,  0. 

The  special  applications  of  this  method,  as  well  as  of  those  which 
will  follow,  are  indicated  in  Part  Third. 

MULLER'S  FLUID  (MODIFIED).* 

Bichromate  of  potash,  ....         25  grammes. 
Sulphate  of  copper,    ...         .  5          " 

Water, 1,000  c.c.      M. 

This  may  be  employed  in  precisely  the  same  manner  as  the  dilute 
chromic-acid  solution. 

DECALCIFYING   PROCESS. 

6fc  Chromic  acid  solution,    .         .  '  ..         9  parts. 

Citric  acid,  C.  P.,    .         .         .         .         .  1  part. 

Water, .         .90  parts. 

The  earthy  salts  may  be  removed  from  teeth  and  small  pieces  of  bone 
with  a  liberal  supply  of  the  above  in  about  twenty  days.  A  frequent 
change  of  the  solution  will  greatly  facilitate  the  process;  and  an  occa- 
sional addition  of  a  few  drops  of  the  nitric  acid  may  be  made,  with  very 
dense  bone.  After  the  removal  of  the  lime  salts,  the  pieces  may  be 
preserved  in  alcohol  until  such  time  as  sections  are  needed,  when  they 
may  be  cut  with  the  microtome  without  injury  to  the  knife. 

DISSOCIATING    PROCESS    (W.    STIRLING). 

Artificial  Gaslric  Fluid. 

Pepsin, 1  gramme. 

Hydrochloric  acid,         .         .         .         .  1  c.c. 

Water,      .       • 500  c.c.    M. 

This  process  depends  for  its  value  upon  the  fact  that  certain  con- 
nective tissues  are  more  rapidly  dissolved  by  the  fluid  than  others. 

BAYBERRY   TALLOW,    HARDENING    OR   INFILTRATING    PROCESS. 

Some  three  years  since,  I  devised  a  method  of  infiltrating  tissues 
with  bayberry  tallow.  Tissues  like  lung,  etc.,  which  are  delicately 

*  The  original  Muller's  fluid  consists  of  the  above  (minus  the  copper  salt) 
with  an  addition  of  12.5  grammes  of  sulphate  of  soda. 


CELLOIDIN    INFILTRATION.  ^# 

cellular  and  hence  very  difficult  to  cut,  when  infiltrated  with  this 
material  are  supported  in  such  a  manner  as  to  render  the  production 
of  thin  sections  a  very  easy  matter. 

Bayberry  tallow  is  found  in  commerce  in  various  grades.  The  best 
is  white,  clean,  and  of  a  consistency  about  equal  to  that  of  hard  mut- 
ton tallow.  It  is  instantly  soluble  in  benzol,  and  dissolves  rather 
slowly  in  alcohol. 

Having  selected  a  piece  of  alcohol-hardened  tissue  for  cutting,  care- 
fully wipe  it  dry  with  blotting-paper  and  drop  it  into  a  capsule 
containing  melted  bay  berry  tallow.  In  order  to  render  the  tallow 
sufficiently  fluid,  and  yet  prevent  the  heat  from  becoming  great 
enough  to  injure  the  tissue,  the  capsule  should  be  set  over  a  water- 
bath.  Bubbles  immediately  arise  as  the  spirit  is  vaporized  and  the 
tallow  gradually  fills  the  interstices  of  the  tissue.  If  the  latter  be  of 
a  somewhat  dense  character  it  will  be  best,  before  placing  it  in  the  tal- 
low, to  allow  it  to  remain  for  an  hour  in  pure  benzol  which,  evaporating 
at  a  very  low  temperature,  gives  more  ready  admission  to  the  infiltrat- 
ing medium. 

The  length  of  time  required  for  complete  infiltration  will  depend 
upon  the  density  and  the  degree  of  heat  employed.  Usually  from  ten 
to  thirty  minutes  will  suffice. 

The  tissue,  having  become  sufficiently  infiltrated,  is  lifted  out  with 
the  forceps,  placed  on  a  cork  support,  and  allowed  to  cool.  It  is  then 
cut,  either  free-handed  or  with  the  microtome,  and  ivithout  alcohol. 
The  dry  sections,  resembling  tallow  or  wax  shavings,  are  brushed  into 
a  saucer  of  pure  benzol  when  in  a  moment  the  tallow  will  be  dis- 
solved from  the  tissue.  The  sections  are  then  lifted  with  a  needle 
singly  into  a  saucer  of  alcohol  to  remove  the  benzol.  Afterward, 
they  are  transferred  to  a  bottle  of  spirit,  and  labelled  for  future  use. 
They  will  keep  indefinitely. 

This  process  is  peculiarly  advantageous  with  such  tissues  as  lung, 
pancreas,  cerebellum,  intestine,  etc.,  where  the  structures  require 
support  only  while  they  are  being  cut.  The  infiltrated  blocks  of  tis- 
sue can  be  kept  dry  until  such  time  as  they  may  be  wanted. 

CELLOIDIN    INFILTRATION. 

Certain  structures  require  permanent  support,  i.  e.,  not  only  while 
being  cut,  but  during  the  subsequent  handling  of  the  sections.  The 
celloidin  infiltrating  process  is  best  adapted  to  such  material.  Con- 
siderable time  is  needed  for  the  successful  employment  of  the  process, 
but  results  can  be  secured  that  cannot  be  equalled  with  any  other 
method. 


24  PRACTICAL     MICROSCOPY. 

Celloidin  is  the  proprietary  name  of  a  sort  of  pyroxylin,  very  solu- 
ble in  a  mixture  of  ether  and  alcohol,  producing  a  collodion.  If 
thick  collodion  be  exposed  for  a  few  moments  to  the  air  it  becomes 
semi-solid — not  unlike  boiled  egg-albumen;  and  to  this  property  is  due 
the  value  of  a  solution  of  celloidin  in  histology.  It  may  be  used  as 
follows: 

To  a  mixture  of  equal  parts  of  ether  and  alcohol  add  celloidin,* 
until  the  thickest  possible  solution  has  been  obtained. 

A  piece  of  alcohol-hardened  tissue  having  been  selected  and  kept 
for  the  preceeding  twenty-four  hours  in  a  mixture  of  equal  parts  of 
alcohol  and  ether,  is  placed  in  about  an  ounce  of  the  solution,  and 
allowed  to  remain  twenty-four  hours.  The  bottle  containing  the 
whole  should  be  well  corked  to  prevent  evaporation. 

The  tissue  after  infiltration  is  to  be  placed  on  a  cork  support  and 
allowed  to  remain  in  the  open  air  for  a  few  minutes,  after  which  it 
should  be  plunged  into  a  mixture  of  alcohol  two  parts,  water  one 
part.  Here  it  may  remain  for  twenty-four  hours,  or  until  wanted. 

Cut  in  the  usual  way  using  a  mixture  of  alcohol  two  parts,  water  one 
part,  for  flooding  the  knife;  the  sections  should  be  finally  preserved  in 
the.  same  instead  of  pure  alcohol  which  would  dissolve  the  celloidin. 

In  infiltrating  the  tissue  with  the  collodion  it  is  best,  especially  if 
it  be  very  dense  in  parts,  to  use,  first,  a  thin  and  subsequently 
the  thick  solution.  A  more  perfect  infiltration  is  often  obtained  in 
this  way.  In  some  cases  I  have  been  obliged  to  continue  the  m acera 
tion  for  several  days.  The  solution  should  be  kept  in  well-stoppered 
bottles,  as  the  ether  is  exceedingly  volatile.  Should  the  collodion  at 
any  time  become  solid  from  evaporation,  it  may  be  easily  dissolved 
by  adding  the  ether  and  alcohol  mixture. 

The  process  is  of  inestimable  value  where  delicate  parts  are  weakly 
supported,  and  where  it  is  important  to  preserve  the  normal  relations. 
The  gelatin-like  collodion  permeates  every  space  and,  as  it  is  not  to  be 
removed  in  the  future  handling  of  the  sections,  it  affords  a  support  to 
portions  that  would  otherwise  be  lost  or  distorted.  It  offers  no  ob- 
struction to  the  light,  being  perfectly  translucent  and  nearly  colorless. 

HARDENING   BY   FREEZING,    ETC. 

I  do  not  recommend  the  freezing  process. 

Other  fixing  and  hardening  methods,  which  are  of  special  applica- 
tion only,  will  be  introduced  in  our  future  work  as  occasion  may  de- 
mand. 

*  I  find,  after  repeated  trial,  that  the  ordinary  soluble  gun-cotton,  such  as  is 
employed  by  photographers,  is  in  no  way  inferior  to  the  celloidin. 


STAINING   AGENTS    AND   METHODS.  25 

STAINING  AGENTS   AND    METHODS. 

STAINING   FLUIDS. 

It  is  a  very  interesting  fact  (and  one  upon  which  our  present 
knowledge  of  histology  largely  depends)  that,  on  examination  of  tis- 
sues which  have  been  dyed  with  special  colored  fluids,  the  dye  will 
be  found  to  have  colored  certain  anatomical  elements  very  deeply, 
others  slightly,  while  others  still  remain  unstained.  Not  only  are 
different  depths  of  color  thus  obtained,  but  different  tints,  even  with 
a  single  dye,  are  often  presented.  If  a  section  of  some  animal  tissue 
be  immersed  in  a  mordanted  solution  of  logwood,  for  example,  besides 
the  different  depths  of  blue  which  are  communicated  to  certain 
parts,  other  elements  present  pink  and  violet  tints  in  various  shades. 

The  rule  concerning  the  selection  of  dyes  seems  to  be  that  those 
elements  of  a  tissue  which  are  the  most  highly  endowed  physio- 
ogically  take  the  staining  most  readily.  The  minute  granules  of 
nuclei  are  so  deeply  stained  in  the  logwood  dye  as  to  appear  almost 
black.  The  nuclei  are  plainly  stained,  while  the  limiting  membrane 
of  cells  is  usually  but  slightly  colored.  Old,  dense  connective  tis- 
sues stain  feebly,  or  fail  entirely  to  take  color.  The  differentiation 
is,  without  doubt,  due  to  chemical  action  between  the  elements  of 
the  dye  and  those  of  the  tissue. 

A  very  great  number  and  variety  of  materials  have  been  used  for 
histological  differentiation,  and  a  simple  enumeration  of  them  all 
would  very  nearly  fill  the  remainder  of  our  pages.  It  will  be  found, 
however,  that  leading  histologists  confine  themselves  to  two  or  three 
standard  formulae  for  general  work.  I  shall  notice  only  those 
methods  which  have  been  thoroughly  demonstrated  by  years  of  em- 
ployment as  best  for  the  purpose  suggested.  Special  cases  will  re- 
quire special  treatment,  which  will  be  indicated  in  proper  connection. 

H^MATOXYLIN  *    STAINING   FLUID. 

To  about  eight  fluid-ounces  of  a  hot,  saturated  aqueous  solution 
•of  common  alum,  contained  in  a  porcelain  capsule,  add,  a  few  grains 
at  a  time,  one  drachm  of  hcematoxylin,  with  constant  stirring.  Boil 
over  the  spirit  lamp  very  slowly  for  fifteen  minutes.  Add  sufficient 
water  to  compensate  for  evaporation;  and,  when  cold,  pour  into  a 
wide-mouth  bottle.  Throw  in  a  piece  of  camphor,  say  30  grains, 

*  The  coloring  principle  of  the  Hsematoxylon  Campechianum.  Merck's  pre- 
paration should  be  used. 


26  PRACTICAL   MICROSCOPY. 

allow  the  whole  to  remain  exposed  to  the  air  for  one  week,  and  thea 
filter. 

The  solution  should  always  be  filtered  before  using.  Keep  the 
filter  paper  in  a  funnel,  and  use  it  as  a  stopper  for  the  bottle.  The 
dye  improves  in  strength  of  color  for  two  or  three  weeks. 

Should  the  solution,  which  is  of  a  beautiful  purple  or  violet  color, 
at  any  time  turn  red,  a  small  piece  of  common  chalk  may  be  added. 
This  will  restore  the  color  by  neutralizing  the  acidity.  A  few  crystals 
of  alum  should  always  be  kept  in  the  bottle  to  insure  saturation. 

Prepared  as  above,  the  dye  will  keep  perfectly  for  at  least  eight 
months,  and  gives  a  permanent  stain. 

BOKAX-CARMINE   STAINING   FLUID. 

To  eight  ounces  of  a  saturated  aqueous  solution  of  borax  (borate 
of  soda)  add  one  drachm  of  the  best  No.  40  carmine  (previously 
rubbed  into  a  paste  with  a  little  water).  In  order  to  insure  satura- 
tion, some  borax  crystals  should  always  be  left  undissolved  at  the 
bottom  of  the  bottle.  Agitate  frequently,  and,  after  twenty-four 
hours,  add  fifteen  drops  of  liquor  potass®. 

Always  filter  or  decant  before  using.  It  will  keep  indefinitely,  im- 
proving, to  a  certain  extent,  with  age. 

EOSIN   SOLUTION. 

Alcohol, 2  ounces. 

Eosin, 1  drachm. 

This  will  give  a  saturated  solution. 

PICRIC    ACID    SOLUTION. 

Picric  acid, i  ounce. 

Water, 4  ounces. 

The  acid  is  in  excess,  insuring  saturation. 

NITRATE    OF   SILVER    SOLUTION. 

Nitrate  of  silver, o  grains. 

Distilled  water,          ....  4  ounces. 

If  the  water  be  pure,  light  will  have  no  effect  upon  the  solution. 


STAINING   METHODS.  27 

STAINING  METHODS. 

H^MATOXYLLtf    STAINING    PROCESS. 

You  will  require  for  future  work  a  needle  like  Fig.  13,  several 
saucers,  preferably  of  white  ware;  a  few  watch-glasses—large,  odd 
sizes  are  usually  cheaply  obtainable  at  the  jewellers;  half  a  dozen 
glass  salt-cellars — small  ones  known  as  "individual  salts;"  and  a 
two-ounce,  shallow,  covered  porcelain  box,  such  as  druggists  use 
for  ointments,  dentifrices,  etc. 

Place  on  the  work-table  (best  located  so  as  to  be  lighted  from  your 
side  and  not  from  the  front)  in  order,  as  in  Fig..  14. 

1.  A  wa/ch-glass,  containing  say  fl.  3  ij.  of  haematoxylin  fluid. 

2.  Saucer,  filled  with  water. 

3.  Salt-cellar,  filled  with  alcohol. 

4.  The  covered  porcelain  box,  containing  about  an  ounce  of  oil  of 
cloves.* 


FIG.  13.— NEEDLE  FOR^LIFTING  SECTIONS,  ETC. 

Select  a  section  from  some  one  of  your  stock  bottles,  lifting  it  out 
with  the  needle,  and  place  it  in  the  haema.  solution.  The  section 
having  been  taken  from  alcohol  and  transferred  to  an  aqueous  staining 
fluid,  will  twirl  about  on  the  surface  of  the  latter,  inasmuch  as  cur- 
rents are  formed  by  the  union  of  the  water  and  the  spirit. 

"How  long  shall  I  let  the  section  remain  in  the  haema. ?"  The 
only  answer  I  can  give  is,  "  Until  properly  stained!  "  Nothing  but 
experience  will  give  you  any  more  definite  information.  Much  de- 
pends upon  some  peculiar  property  in  the  tissues:  some  stain  rapidly, 
others  stain  very  slowly.  The  strength  of  the  dye  is  another  deter- 
mining factor.  Usually  with  the  haema.  formula,  as  given,  from  six 
to  ten  minutes  will  suffice. 

Place  the  needle  under  the  section  (if  the  fluid  be  so  opaque  as  to 
hide  the  tissue,  place  the  watch-glass  over  a  piece  of  white  paper  or 
a  bit  of  mirror),  and  gently  lift  it  out;  drain  off  the  adhering  drop  of 
dye  on  the  edge  of  the  glass,  and  drop  into  the  saucer  of  water.  Here 
we  can  judge  as  to  the  color,  and  we,  perhaps,  find  it  to  be  of  a  light 

*  The  oil  of  Bergamot  must  be  used  for  clarifying  sections  which  have  been 
infiltrated  with  collodion,  as  the  clove  oil  is  a  solvent  of  the  pyroxyline. 


PRACTICAL    MICROSCOPY. 


purple — too  light;  so  you  may  return  it  to  the  haema.  for  another 
period  of  two  or  three  minutes,  which  will  probably  give  sufficient 
•depth. 

As  the  section  floats  on  the  washing  water,  you  will  notice  that  the 
latter  will  be  colored  by  the  dye,  some  of  which  leaves  the  tissue. 
Allow  the  water  to  act  until  no  more  color  comes  out.  The  tint  of 
the  section  changes  from  purple  to  violet,  and  the  water  must  be  al- 
lowed to  act  until  the  change  is  complete.  Again,  you  will  remem- 
ber that  this  dye  contains  alum  and,  if  you  hurry  the  washing,  you 
will  undoubtedly  find  crystals  covering  your  specimen  after  it  has 
been  mounted.  From  five  to  ten  minutes  will  complete  the  washing. 

If  you  were  to  examine  your  section  at  this  stage,  you  would  find  it 
opaque,  and,  as  we  are  obliged  to  study  our  objects  mainly  by  trans- 
mitted light,  we  must  find  some  means  of  securing  translucency. 
The  essential  oils  are  used  for  this  purpose,  oil  of  cloves  being  com- 
monly employed.  Lift  the  section  from  the  water  with  the  needle; 
let  it  drain  a  moment,  and  then  drop  it  into  the  alcohol  with  which 
the  salt-cellar  was  filled.  The  object  of  this  bath  is  the  removal  of 
the  water  from  the  tissue,  and  this  will  be  accomplished  in  from  five 
to  ten  minutes.  Again  lift  the  section,  and  place  it  in  the  oil  of 
cloves.  The  tissue  floats  out  flat,  and  in  a  few  minutes  sinks  in 
the  oil. 

We  might  proceed  to  the  examination  of  the  stained  section;  but  I 
shall  ask  you  to  let  it  remain  in  the  oil,  covering  the  box  carefully  to 
exclude  our  great  enemy,  the  dust,  until  we  have  learned  more  about 
staining. 


FIG.  14.—  DIAGRAM  INDICATING  THE  SUCCESSIVE  STEPS  IN  STAINING  WITH   THE   H.EMATOXYLIN 

SOLUTION. 

To  recapitulate:     The  essential  steps  in  the  haema.  process  are: 

1.  Staining  the  tissue — haema. 

2.  Washing — water. 

3.  Dehydrating — alcohol. 

4.  Rendering  translucent — oil  of  cloves. 


STAINING    METHODS.  2if 

As  the  section  is  put  in  the  dye,  care  should  be  taken  to  so  float  it 
out  that  it  may  not  be  curled.  This  is  easily  done  with  the  needle. 
After  the  alcohol  bath,  however,  this  becomes  difficult,  as  the  tissue 
is  rendered  stiff  by  the  removal  of  the  water. 

This  is  the  simplest  and  best  of  all  methods  for  general  work,  and 
you  are  advised  to  master  every  detail  of  the  process.  After  reading 
the  directions  which  I  have  given,  and  having  never  seen  the  work 
actually  done,  you  will  not  be  singular  if  you  conclude  the  staining 
of  tissues  to  be  a  tedious  and  slow  process;  but  after  a  month's  work 
you  will  be  able  to  stain  fifty  different  sections  in  half  an  hour,  and 
have  them  ready  for  mounting. 

H^MATOXYLIN   AND   EOSIN.       DOUBLE   STAINING. 

Very  beautiful  and  valuable  results  in  differentiation  are  obtained 
by  staining  first  with  hasma.  and  subsequently  with  eosin.  Eosin  is  a 
salt  of  resorcin,  staining  most  animal  tissues  pink,  and  it  affords  with 
the  haema.  a  good  contrasting  color.  The  tissue  is  to  be  stained  in 
haema.  and  washed  in  water  as  usual;  then  it  is  placed  in  the  eosin 
solution,  and  afterwards  washed  again.  The  subsequent  treatment 
is  as  with  the  plain  haema.  process,  viz.,  dehydration  with  alcohol, 
after  which  the  oil  of  cloves. 


FIG.  15.— DIAGRAM  INDICATING  THE  SUCCESSIVE  STEPS  IN  DOUBLE  STAINING  WITH 


.  AND  EOSIN. 


The  diagram,  Fig.  15,  shows  the  process  complete: 

1.  Watch-glass  with  haema. 

2.  Saucer  with  water. 

3.  Watch-glass  two- thirds  filled  with  water,  witli  five  drops  of  eosin 
solution  added. 

4.  Saucer  containing  water. 

5.  Salt-cellar  filled  with  alcohol. 

6.  Covered  oil-dish. 

The  eosin  stains  very  quickly,  generally  in  about  a  minute.  Care 
should  be  taken  not  to  overstain  with  it,  as  it  cannot  be  washed  out. 
If  the  sections  are  found  at  any  time  to  be  overstained  with  haema. 
the  color  may  be  removed  to  any  desired  extent  by  floating  them  in  a 


30 


PRACTICAL    MICROSCOPY. 


saturated  aqueous  solution  of  alum.     They  must  afterward  be  washed 
in  clean  water. 

BORAX-CARMIKE  STAIKING    PROCESS. 

Arrange  your  materials  as  in  the  diagram,  Fig.  16. 

1.    Watch-glass  two-thirds  filled  with  the  carmine  fluid. 

3.  Saucer  containing  about  an  ounce  of  alcohol. 

3.  Salt-cellar  filled  with  a  saturated  solution  of  oxalic  acid  in  al- 
cohol. 

4.  Salt-cellar  with  alcohol. 

5.  Porcelain  dish  containing  oil  of  cloves. 

The   carmine  solution  will  stain  ordinarily  in  from  three  to  ten 
minutes.     After  the  section  has  been  for  a  few  minutes   in  the  dye, 


FIG.  16.— DIAGRAM  INDICATING  THE  SUCCESSIVE  STEPS  IN  STAINING  WITH  BORAX-CARMINE. 


you  will  lift  it  with  the  needle,  drain,  and  transfer  to  the  saucer  con- 
taining alcohol.  You^will  then  be  enabled  to  determine  whether  the 
section  is  sufficiently  stained;  it  should  be  a  deep,  opaque  red.  The 
alcohol  washes  off  the  section,  removing  the  adhering  solution  of 
carmine. 

The  carmine  must  now  be  fixed  in  the  tissue  or  mordanted;  and 
this  you  proceed  to  do  by  transferring  the  section  to  the  watch-glass 
of  oxalic  acid  solution.  Notice  the  change  in  color,  from  a  dull  red 
to  a  bright  crimson,  and  when  the  change  is  complete,  lift  it  into  the 
salt-cellar  containing  clean  alcohol.  This  dissolves  out  the  acid, 
which,  if  left,  would  appear  later  on  the  specimen  in  crystals.  Five 
minutes  suffice  for  this  washing,  after  which  transfer  to  the  oil  of 
cloves. 

This  process  does  not  give  as  sharp  contrasts  as  the  haema.  and 
eosin,  but  it  is  simpler  and  very  permanent.  It  is  best  to  select 
3ome  one  process  for  general  work,  and  adhere  to  it.  The  acid  of  the 
Carmine  process  must  be  guarded  with  extreme  care,  as  the  smallest 
particle  is  sufficient  to  spoil  the  hsema.  solution.  Look  to  it  that  the 


MOUNTING   OBJECTS.  31 

dishes  are  kept  scrupulously  clean,  and  the  same  care  must  be  be- 
stowed upon  the  needles,  forceps,  etc. 

You  may,  of  course,  stain  several  sections  at  once,  providing  you 
take  care  to  keep  them  from  rolling  up  or  sticking  together. 

While  the  vessels  which  I  have  recommended  will  be  found  of  con- 
venient, proportionate,  and  economical  size  for  general  work,  larger 
ones  are  sometimes  needed;  and  almost  any  glass  or  porcelain  vessel 
may  be  impressed  for  duty. 

CARMINE    AND   PICRIC   ACID   STAINING. 

After  having  washed  the  tissue,  subsequently  to  mordanting  with 
oxalic  acid  in  the  borax- carmine  process,  a  bright  yellow  may  be 
communicated  to  certain  anatomical  elements  by  means  of  picric  acid. 
This  often  gives  a  valuable  differentiation. 

The  sections  are  placed  in  the  picric-acid  solution  and  allowed  to 
remain  for  ten  minutes.  Kemove  to  water  one  ounce,  glacial  acetic  acid 
ten  drops  for  a  moment,  to  fix  the  yellow;  after  this  dehydrate  with 
alcohol,  and  clarify  with  oil  of  cloves  as  usual.  The  sections  should 
be  transferred  to  the  picric  and  acetic  acid  solutions  by  means  of  a 
platinum  wire  or  a  minute  glass  rod.  The  ordinary  needle  would  be 
corroded,  and  the  sections  thereby  discolored. 

MOUNTING  OBJECTS. 

CLEANING   SLIDES   AND   COVERS. 

When  purchasing  "slides,  let  me  urge  you  to  get  them  of  good 
quality.  The  regular  size  is  one  by  three  inches,  and  the  edges 
should  be  smoothed.  As  furnished  by  the  dealers  they  are  usually 
quite  clean,  and  only  require  rubbing  with  a  piece  of  old  linen  to 
prepare  them  for  use. 

The  cover-glasses  should  be  thin,  not  over  TJ^th  of  an  inch,  called 
in  the  trade-lists  "  No  1."  Circles  or  squares  three-quarters  of  an 
inch  in  diameter  are  generally  convenient.  They  must  be  thoroughly 
cleaned:  Drop  them  singly  into  a  saucer  containing  hydrochloric 
acid.  Then  pour  off  the  acid,  and  let  clean  water  run  into  the  dish 
for  several  minutes.  Drain  off  the  water  and  pour  an  ounce  of  alco- 
hol on  the  covers.  Kemove  them  one  at  a  time  with  the  forceps  or 
needle,  and  wipe  dry  with  old  linen.*  The  glass  may  be  held  between 

*  We  are  indebted  to  Professor  Gage,  of  Cornell  University,  for  suggesting 
the  use  of  Japanese  tissue  paper  for  wiping  cover  glasses,  lenses,  etc.  Or- 
dinary manilla  toilet  paper  is  also  an  excellent  material  for  such  work. 


32  PRACTICAL   MICROSCOPY. 

the  thumb  and  forefinger,  the  linen  being  interposed.  Very  slight 
pressure  and  rubbing  will  complete  the  process.  The  surface  of  the 
glasses  should  be  brilliant,  and  they  are  to  be  preserved  for  future  use 
in  a  dust-tight  box. 

TRANSFERRING   THE   SECTIONS   TO   THE    SLIDE. 

Procure  a  piece  of  either  very  thin  sheet  copper  or  heavy  tin  foil, 
three  inches  long  and  one-half  inch  wide,  and  bend  it  about  three- 
fourths  of  an  inch  from  one  end,  making  a  section  lifter  as  shown  in 
Pig.  17. 


FIG.  17. — SECTION  SPOON. 

Strip  of  copper  or  heavy  tin  foil,  best  for  lifting  sections  from  staining  and  other  fluids.    For 
use  in  fluids  which  would  attack  metals,  the  spoon  should  be  constructed  from  horn. 

Place  a  clean  slide  on  the  table  before  you  and  with  the  section - 
lifter  used  like  a  spoon  dip  up  one  of  the  sections  from  the  clove-oil. 
By  inclining  the  lifter,  the  section  may  be  made  to  float  to  the  centre 
of  the  slide.  A  small  sable  brush  is  often  convenient  for  coaxing  the 
section  off  the  lifter. 

If  it  were  our  present  object  to  simply  examine  the  section,  we 
could  drop  a  thin  cover-glass  on  the  specimen,  and  it  would  be  ready 
for  study.  Such  an  object  would  afford  every  requirement  for 
present  observation,  but  would  nofc  be  permanent.  The  oil  of  cloves 


TRANSFERRING    SECTIONS    TO    THE    SLIDE. 


33 


would  evaporate  after  a  few  days  and  the  section  be  ruined.     We  pro- 
ceed to  make  a  permanent  mounting  of  our  object. 

The  clove  oil,  surrounding  the  section  on  the  slide,  is  first  to  be  re- 
moved; and  it  can  easily  be  done  by  means  of  blotting-paper.  With 
a  narrow  slip  of  thin  filter  paper  wipe  up  the  oil,  exercising  care  not 
to  touch  the  section  or  it  will  become  torn.  Proceed  carefully, 
taking  fresh  paper  until  the  oil  will  no  longer  drain  from  the  section 


FIG.  18  —METHOD  OF  LABELLING  A  MOUNTED  SPECIMEN. 

when  the  slide  is  held  vertically.  With  a  glass  rod  remove  a  little  of 
the  dammar  solution  (vide  formulae)  from  the  bottle  and  allow  a 
drop  of  this  varnish  to  fall  upon  the  section. 

Pick  up  a  clean  cover-glass  with  a  needle,  and  place  it  on  the  drop 
of  dammar.  This  operation  is  seen  in  Fig.  18.  The  point  of  the 
needle  may  be  placed  beneath  the  cover-glass,  the  tip  of  the  forefinger 


FIG.  19. — MODE  OF  HANDLING  THE  COVER-GLASS  IN  MOUNTING  TISSUES. 

pressing  lightly  over  it,  and  you  will  be  enabled  to  carry  the  thin 
glass  wherever  desired. 

As  the  cover  settles  down  the  air  is  pressed  out,  until  finally  the 
section  appears  imbedded  in  the  varnish— the  latter  filling  the  space 
between  the  cover  and  the  slide. 

The  object  is  "mounted."  You  \\WQ2o  permanent  specimen.  The 
slide  must  be  kept  flat,  as  the  dammar  is  soft.  After  some  weeks, 
3 


34  PRACTICAL   MICROSCOPY. 

the  varnish  around  the  edge  of  the  cover  will  stiffen,  and  eventually 
become  solid.  Do  not  paint  colored  rings  around  the  specimen. 
Nothing  can  present  a  neater  appearance  than  the  simple  mount,  as  I 
have  described  it,  after  having  been  properly  labelled.  Labels 
seven-eighths  of  an  inch  square  may  be  put  on  one  or  both  ends,  with 
the  name  of  the  object,  date,  method  of  staining,  or  whatever  par- 
ticulars you  may  prefer. 

Specimens  should  be  kept  in  trays  or  boxes  so  as  to  always  lie 
flat. 

CARE  OP  THE  MICROSCOPE. 

The  objectives  constitute  the  most  valuable  part  of  the  instrument. 
The  lenses  should  never  be  touched  with  the  fingers;  indeed  the  same 
rule  applies  to  all  optical  surfaces.  When  the  glasses  become  soiled, 
they  may  ce  cleaned,  but  it  should  be  done  with  great  care.  While 
the  effect  of  a  single  cleaning  would  probably  not  be  to  the  slightest 
appreciable  injury  to  the  glass,  repeated  wiping  with  any  material, 
however  soft,  will  destroy  the  perfect  polish,  and  result  in  obstruction 
of  light  and  consequent  dimness  in  the  field.  Never  use  a  chamois 
leather  on  an  optical  surface,  as  these  skins  contain  gritty  particles. 
Old,  well-worn  linen  and  Japanese  paper  are  by  far  the  best  mate- 
rials for  wiping  glasses.  If  a  lens  be  covered  with  dust,  brush  it 
off  ;  breathe  on  the  surface,  and  wipe  gently  with  the  linen  or  paper. 
Should  you  get  clove  oil  on  the  front  lens  of  the  objective  (as  fre- 
quently happens  when  examining  temporary  mounts)  wipe  it  dry  and 
then  clean  with  the  linen  moistened  with  a  drop  of  alcohol.  Dammar 
varnish  can  be  very  readily  removed  from  any  surface  after  having 
softened  it  with  oil  of  cloves.  The  front  lens  of  the  objective,  being 
the  only  one  exposed,  is  the  one  usually  soiled. 

Particles  of  dirt  on  the  objective,  as  I  have  said,  cause  a  dimness  in 
the  field — the  image  is  blurred.  Dust  on  the  lenses  of  *t he  eye-piece, 
however,  appears  in  the  field.  These  lenses  are  readily  cleaned  by 
dusting,  and  wiping  with  the  linen,  after  having  breathed  on  the 
surface.  Never  wipe  a  lens  when  dusting  with  a  camel's  hair  brush 
will  answer  the  purpose. 

The  microscope  should  either  be  covered  with  a  shade  or  cloth,  or 
put  away  in  its  case,  when  not  in  use.  The  delicate  mechanism  of  the 
fine  adjustment  becomes  worn  and  shaky  if  not  kept  free  from  dirt. 


PART   SECOND. 


STRUCTURAL    ELEMENTS, 


PRELIMINARY   STUDY. 

FOKM    OF   OBJECTS. 

From  a  single  and  hasty  view  of  bodies  under  the  microscope,  we 
are  liable  to  form  erroneous  ideas  of  form.  Either  a  sphere,  disc, 
ellipsoid,  ovoid,  or  cone  may  be  so  viewed  as  to  present  a  circular  out- 
line. It  therefore  becomes  important  to  view  objects  in  more  than, 
a  single  position.  This  can  easily  be  accomplished  with  isolated 
particles  by  suspension  in  a  liquid.  In  this  way  the  true  shape  of  a 
blood -corpuscle,  e.  g.,  may  be  determined. 

Again,  much  information  concerning  the  actual  form  of  bodies  may 
be  gained  by  a  proper  adjustment  of  the  fine  focussing  screw.  You 
may  remember  that  the  depth  of  the  field  of  view  in  the  microscope 
is  exceedingly  slight.  Speaking  accurately,  only  a  single  plane  can  be 
seen  with  a  single  focal  adjustment;  but  by  gradually  raising  or  low- 
ering the  tube  of  the  microscope,  the  different  parts  of  a  body  maybe 
focussed  and  studied  and  an  accurate  idea  of  form  secured. 

With  a  glass  rod  place  a  drop  of  milk,  which  has  previously  been 
diluted  with  three  parts  of  water,  on  a  slide,  and  put  a  cover-glass 
thereon  as  in  Fig.  19.  Focus  first  with  the  low  power  (L).  A  mul- 
titude of  minute  dots  are  observed.  Then  switch  on  the  high  power 
(H),  and  the  dots  will  resolve  into  circular  figures.  Select  one  of  the 
smaller  particles  and,  as  you  raise  the  focus,  the  centre  of  the  figure 
retains  its  brilliancy,  while  the  edges  become  dark  or  blurred,  show- 
ing convexity.  Reverse  the  focus,  and  the  centre  again  retains  its 
sharpness  long  after  the  edge  has  become  blurred.  The  figure,  then, 


'36 


PRACTICAL    MICROSCOPY. 


is  a  spheroid.  These  bodies  are  fat  globules.  Particles  of  free  fat 
always  assume  the  spheroidal  form  when  suspended  in  a  liquid. 

Note  the  larger  globules;  they  have  become  flattened  by  pressure  of 
the  cover-glass. 

Clean  the  slide,  and  make  a  second  preparation  from  the  diluted 
milk— first,  however,  shaking  it  violently  in  a  bottle.  Note  the  flat- 
tened air  bubbles  among  the  oil  globules.  Observe  that  these  air 


A| 


FIG.  20.— DIAGRAM  SHOWING  "THE  EFFECT  OF  AIR  BUBBLES  AND  OIL  GLOBULES  IN  A  MOUNTED 
SPECIMEN  UPON  THE  RAYS  OF  LIGHT. 

The  lines  A,  B,  show  the  refraction  of  the  rays  (so  as  to  produce  a  ring  of  color)  by  the  action 
of  two  plano-concave  water  lenses  which  are  formed  by  the  air-bubble. 

The  oil  is  seen  to  correct  the  refraction  cf  C  D,  thus  giving  but  little  color  to  the  margin  of 
this  globule. 

bubbles  have  no  intrinsic  color,  while  the  fat  globules  are  faintly 
yellow.  Observe  the  change  in  the  ring  of  prismatic  color  about  the 
edge  of  the  air  bubble,  as  the  focus  is  altered.  No  such  color  will  be 
.seen  in  connection  with  the  oil  globule. 

The  bubbles  assume  various  figures  from  pressure  of  the  cover  glass. 


MOVEMENT   OF   OBJECTS. 

Objects  are  frequently  seen  moving  in  the  field  of  the  microscope, 
the  movement  being  magnified  equally  with  their  dimensions. 

Thermal  Currents. — When  with  the  previous  specimen,  or  any 
other  fluid  mount,  the  warm  hand  is  brought  close  to  one  side  of  the 
stage,  the  globules  in  the  field  will  be  seen  swimming  more  or  less 
rapidly.  These  currents  are  due  to  the  unequal  heating  of  the  liquid 
under  observation.  The  direction  of  the  current  is  in  the  reverse  of 
its  apparent  motion. 

Brownian  Movement. — Place  a  fragment  of  dry  carmine  on  a  slide; 
add  a  drop  of  water,  and  with  a  needle  stir  until  a  paste  is  formed. 
Add  another  drop  of  water,  and  immediately  put  on  the  cover- glass. 
With  H,  note  the  most  minute  particles,  and  observe  their  peculiar, 
dancing  motion.  This  occurs  when  almost  any  finely-divided  and 
generally  insoluble  solid  is  mixed  with  water;  it  ceases  after  a  short 
time.  The  movement  has  been  attributed  to  several  causes. 


EXTRANEOUS    SUBSTANCES. 


3T 


Vital  Movements. — Place  a  drop  of  decomposing  urine  on  a  slide, 
cover  and  focus  with  H.  The  field  contains  innumerable  minute 
spherules  and  rods  (bacteria)  which  are  in  active  motion,  resembling 
somewhat  the  Brownian  movement,  although  sufficiently  distinctive 
after  close  observation. 

After  having  rubbed  the  tongue  for  a  moment  against  the  inner 
surface  of  the  cheek,  put  a  drop  of  saliva  on  a  slide,  cover  and  focus 
H.  Among  the  numerous  thin,  nucleated  scales  and  debris,  small 
granular  spherules — the  salivary  corpuscles — will  be  found.  Select 
one  of  the  last,  centre,  and  focus  H.  with  extreme  care.  The  minute 
granules  within  the  cells  are  in  active  motion,  resembling  the  Brown- 
ian movement;  but  with  proper  conditions  the  motion  may  continue 
for  many  hours. 

EXTRANEOUS    SUBSTANCES. 

Before  we  begin  the  study  of  animal  tissues,  I  wish  to  have  you  be- 
come somewhat  familiar  with  the  appearance  of  certain  objects  which 


FIG.  21.— EXTRANEOUS  SUBSTANCES. 

A.  Cotton  fibres,  showing  the  characteristic  twist. 

B.  Linen  fibres,  with  transverse  markings  indicating  segments. 

C.  Wool.    The  irregular  markings  are  produced  by  the  overlapping  of  flattened  cells.    Wool 
may  be  distinguished  from  other  hairs  by  the  swellings  which  appear  at  irregular  intervals  in 
the  course  of  the  former. 

D.  Silk.    Smooth  and  cylindrical. 

are  frequently,  through  accident  or  carelessness,  and  often  in  spite  of 
the  utmost  care,    found  mixed  with  our  microscopical  specimens. 


00  PRACTICAL    MICROSCOPY. 

Among  the  more  common  objects  floating  in  the  air  and  gaining 
access  to  reagents,  to  subsequently  appear  in  our  mounted  specimens, 
are  the  following: 

Fibres. — Procure  minute  pieces  of  uncolored  linen,  cotton,  wool, 
and  silk.  With  a  needle  in  either  hand,  tease  out  or  separate  a  few 
fibres  on  slides,  add  a  drop  of  water  and  cover.* 

Starch. — Procure  samples  of  wheat,  corn,  potato  and  arrow-root 
starch,  or  scrape  materials  containing  any  one  of  these  substances 


FIG.  22. — EXTRANEOUS  SUBSTANCES. 

A.  Granules  of  potato  starch. 

B.  Corn  starch. 

C.  Wood  fibres.    The  circular  dots  are  peculiar  to  the  tissue  of  cone-bearing  trees. 

D.  Spiral  thread  from  a  tea  leaf. 

E.  Fragment  of  feather. 

with  a  sharp  knife.     To  a  minute  portion  on  the  slide  add  a  drop  of 
water,  cover  and  examine  L  and  H. 

Wood  Shavings,  Feathers,  Minute  Insects,  Portions  of  Larger  In- 

*  These  substances,  as  well  as  most  of  those  which  follow  under  the  same 
heading,  may  be  mounted  permanently  as  follows:  Put  the  dry  material  in 
clean  turpentine  for  a  day  or  two,  to  remove  the  contained  air.  Transfer  to 
the  slide,  tease,  separate,  or  arrange  the  elements,  after  which  wipe  away  the 
turpentine  with  strips  of  blotting  paper.  Add  a  drop  of  dammar  and  place 
the  cover-glass  thereon.  The  weight  of  the  cover  will  be  sufficient  to  press  the 
object  flat,  if  it  be  properly  teased  or  separated.  Although  I  do  not  advise  the 
making  of  colored  rings  around  cover -glasses,  they  may  be  formed  after  first 
protecting  the  dammar  with  a  ring  of  gelatin. — Vide  formulae. 


CELLS.  39 

sects,  Pollen,  etc.,  are  easily  mounted  temporarily  or  permanently  as 
above.  They  are  very  commonly  found  in  urine  after  it  has  been  ex- 
posed to  the  air.  and  their  recognition  is  very  important. 

Let  me  urge  you  to  become  familiar  with  the  microscopical  appear- 
ance of  the  commoner  objects  which  surround  us  in  every-day  life. 
The  most  serious  mistakes  have  resulted  from  ignorance  of  this  sub- 
ject. Vegetable  fibres  have  been  mistaken  for  nerves  (!)  and  urinary 
casts,  starch  granules  for  cells,  vegetable  spores  for  parasitic  ova,  etc. 


STRUCTURAL   ELEMENTS. 

Certain  anatomical  structures,  of  a  more  or  less  elementary  nature, 
are  united  in  the  composition  of  organs.  These  structural  elements 
will  with  propriety  first  claim  notice  from  us. 


CELLS. 

A  typical  cell  is  a  microscopical  sphere  of  protoplasm,  constituted 
.as  follows  (vide  Fig.  23): 

A.  Limiting  membrane. 

B.  Cell-body. 

C.  Nucleus. 
JX  Nucleolus. 


0 

FIG.  23.— ELEMENTS  OF  A  TYPICAL  CELL. 


The  wall  consists  of  an  apparently  structureless  membrane   of  ex- 
treme tenuity. 

The  cell-body  may  be  either  clear  (jelly-like),  granular,  or  fibrillated. 
The  nucleus  is  a  minute  spherical  vesicle,  with  a  limiting  mem- 


40  PRACTICAL    MICROSCOPY. 

brane  inclosing  a  clear  gelatinous  material,  traversed  by  a  reticulum 
of  fibrillae. 

The  nucleolus  consists  of  a  spherical  granular  enlargement  upon 
the  fibrillae  of  the  nucleus. 

Deviations  from  the  type  are  most  frequent,  and  vary  greatly  as  to 
form,  number  of  elements,  and  chemical  composition. 


FIG.  24.— A  CELL  NUCLEUS,  WITH  NETWORK  AND  NUCLEOLUS.    DIAGRAMMATIC. 

The  typically  perfect  cell  is  rarely  seen  in  human  tissue  on  account 
of  the  length  of  time  which  commonly  elapses  between  death  and 
observation  of  the  structure,  the  delicate  fibrillae  of  the  nuclei  usu- 
ally appearing  as  a  mass  of  granules. 

CELL   DISTRIBUTION. 

The  complex  mechanism  of  the  body  had  its  origin  in  a  single  cell. 
This  preliminary  structure,  endowed  with  the  power  of  proliferation, 
became  two  cells.  Two  having  been  produced,  they  became  four  ; 
the  four,  eight;  and  thus  progression  advanced  until  they  became 
countless.  Some  of  these  ceils  remained  as  such  ;  others  altered  in 
form  and  composition  gave  birth  to  muscle,  bone,  etc.,  etc.  The 
study  of  these  processes  belongs  to  physiology. 

The  adult  body  is  composed  largely  of  cells  of  various  forms.  The 
different  physiological  processes,  as  secretion,  absorption,  respiration, 
etc.,  are  effected  through  the  intervention  of  these  anatomical 
elements. 

All  free  surfaces,  within  or  without  the  body,  are  covered  ivith 
cells.  The  entire  skin,  the  outside  of  organs,  as  lung,  liver,  stomach, 
intestine,  brain,  etc.,  etc.;  all  cavities,  as  alimentary  tract,  heart, 
ventricles  of  the  brain,  blood-vessels,  ducts,  all  present  a  superficial 
layer  of  cells. 

VARIATION"   IK    FORM    OF   CELLS. 

Alteration  from  the  typical  or  spherical  form  is  effected  mainly 
through  pressure  consequent  upon  active  proliferation  of  contiguous 
cells,  or  growth  of  surrounding  fibrous  tissues. 


SQUAMOUS,    STRATIFIED    AND    TRANSTIONAL    EPITHELIUM.  41 

FLAT   CELLS. 

If  a  cell  be  subjected  to  pressure  on  two  opposite  sides,  a  flattening 
ensues,  and  a  scale-like  element  results.  Flat  cells  are  united  to  form 
a  continuous  structure  in  different  ways. 

SQUAMOUS,    STRATIFIED,    AND   TRANSITIONAL  EPITHELIUM. 

The  simplest  method  of  tissue  production  by  means  of  flat  cells  is 
that  of  superposition,  constituting  squamous  epithelium.  Cells  are 
placed  one  over  the  other,  generally  without  great  regularity.  If 
regular,  and  in  several  layers,  the  structure  is  called  stratified  epithe- 
lium ;  if  only  in  a  few  layers,  it  is  termed  transitional  epithelium. 
The  superficial  layer  of  the  skin  aifords  an  example  of  squamous,. 


FIG.  25.— SQUAMOUS  CELLS  FROM  BUCCAL  EPITHELIUM. 
A.    Typical  cell.    B.    Its  nucleus. 

C.  Union  by  overlapping  forming  laminae. 

D.  Salivary  corpuscles.     X  400. 

stratified  epithelium.     The  bladder,  pelvis  of  the  kidney,  and  vagina 
are  lined  with  transitional  epithelium. 

The  thin,  flat  scales  from  the  mouth  may  be  demonstrated  by 
scraping  a  drop  of  saliva  from  the  tongue  with  the  handle  of  a 
scalpel,  transferring  it  to  the  slide,  and  applying  the  cover.  The 
size  of  the  drop  of  saliva  should  be  carefully  adjusted  so  as  to  fill  the 
space  between  the  cover-glass  and  slide.  Too  little  will  cause  the 
cover  to  adhere  so  tightly  to  the  slide  as  to  press  the  cells  out  of 
form;  too  much,  and  the  saliva  flows  over  the  cover  and  soils  the  ob- 
jective. With  a  glass  rod,  place  a  drop  of  the  dilute  eosin  solution 


42 


PRACTICAL    MICROSCOPY. 


on  the  slide,  and  with  a  needle  lead  it  to  the  edge  of  the  saliva. 
The  dye  will  pass  under  the  cover  slowly;  and,  gradually,  whatever 
anatomical  elements  there  may  be  present  will  be  stained.  Observe 
that  the  nuclei  of  the  flat  scales  first  take  the  dye,  and  appear  of  a 
deep  pink;  while  the  other  portions  are  either  colorless  or  very  lightly 
stained. 

Find  a  typical  field  and  sketch  it  with  pencil,  afterward  tinting 
with  dilute  eosin. 

PAVEMENT    EPITHELIUM. 

When  thin  flat  cells  are  disposed  in  a  single  layer,  like  tiles,  the 
epithelium  is  termed  pavement  or  tessellated.  These  cells  are  often 
•quite  regularly  polygonal  (although  this  obtains  more  frequently  with 
tissue  from  the  lower  animals),  and  they  are  always  connected  by  their 
«dges  by  means  of  an  albuminous  cement. 


FIG.  26.— PAVEMENT  EPITHELIUM.    DIAGRAMMATIC. 

This  structure  is  very  extensively  distributed.  Most  serous  sur- 
faces, e.  g.,  the  pleurae,  omenta.  mesenteries,  and  peritoneal  surfaces 
generally,  are  so  covered.  The  lining  of  the  heart ,  of  arteries  and 
veins,  and  of  lymph  channels  is  constructed  with  these  cemented 
cells.  Blood  capillaries  are  formed  almost  entirely  of  such  elements. 

The  best  demonstration  is  made  by  coloring  the  cement  which 
unites  the  cells.  If  a  tissue,  covered  with  this  epithelium,  be  placed 
for  a  few  minutes  in  a  solution  of  nitrate  of  silver  a  chemical  union 
ensues;  an  albuminate  of  silver  is  formed  which  blackens  in  the  light, 
•thereby  mapping  out  the  cells  with  great  precision  and  clearness. 

It  is  nearly  impossible  to  procure  human  tissue  for  this  purpose,  as 
the  cement  substance  decomposes  soon  after  death.  The  mesentery 
of  the  frog  affords  a  good  example  of  pavement  cell  structure;  and 
-differs  but  little  from  the  arrangement  on  human  serous  surfaces. 


PAVEMENT    EPITHELIUM.  4:6 

Kill  a  large  frog  by  decapitation,  and  open  the  abdomen  freely  by 
an  incision  along  the  median  line.  Pull  out  the  intestines  by  grasping 
the  stomach  with  the  forceps.  This  will  expose  the  small  intestine, 
which  you  will  remove,  together  with  the  attached  mesentery,  by 
means  of  quick  snips  of  the  scissors.  Work  as  rapidly  as  possible  and 
avoid  soiling  the  tissue  with  blood.  Throw  the  gut  into  a  salt-cellar 
filled  with  silver  solution,  vide  formulae,  where  it  must  remain  for  ten 


FIG.  27.    PAVEMENT  EPITHELIUM  FROM  FROG'S  MESENTERY.    SILVER  STAINING. 

A.  Area  showing  the-  outlining  of  the  pavement  cells  by  the  silver-stained  cement  sub- 
stance.   The  nuclei  have  been  brought  out  by  the  carmine.    Minute  stomata  may  be  seen  be- 
tween certain  cells. 

B.  A  blood  capillary  terminating  below  in  an  arteriole.    The  silver  has  outlined  the  en- 
dothelia  of  the  vessels. 

C.  An  area  showing  both  layers  of  the  pavement.    The  deeper  cells  are  faintly  outlined, 
being  out  of  focus.    The  silver  has  been  deposited  over  the  lower  portion  of  the  specimen, 
nearly  obscuring  the  cement  lines.     X  250. 

minutes  covered  from  the  light.  Lift  the  tissue  from  the  solution  by 
means  of  a  strip  of  glass  (or  a  platinum  wire),  and  throw  into  a  saucer 
of  clean  (preferably  distilled)  water,  changing  the  latter  repeatedly  for 
ten  minutes.  After  washing,  and  while  yet  in  the  water,  expose  to 
sunlight  (perhaps  fifteen  minutes)  until  a  brown  tint  is  acquired  which 
indicates  the  proper  staining. 


44  PRACTICAL   MICROSCOPY. 

Proceed  to  stain  the  intestine,  with  mesentery  attached,  with  borax- 
carmine  as  directed  for  sections,  excepting  that,  as  the  mass  is  great, 
it  must  be  washed  twice  in  alcohol  after  the  oxalic  acid. 

We  have  allowed  the  mesentery  to  remain  connected  with  the  gut, 
that  the  former  might  not  curl,  as  it  would  have  done  had  it  been  sep- 
arate. The  preparation  having  reached  the  oil  of  cloves,  proceed  with 
a  pair  of  scissors  to  snip  off  a  small,  flat  piece  of  mesentery.  Remove 
it  to  a  slide,  clean  off  the  oil,  apply  dammar,  and  cover. 

The  mesentery,  you  have  learned  from  descriptive  anatomy,  consti- 
tutes a'support  for  blood  and  lymph  vessels  which  are  in  connection 
with  the  intestine.  The  vessels  are  held  together  with  a  little  deli- 
cate fibrous  (connective)  tissue,  and  are  covered  above  and  below  with 
a  layer  of  pavement  epithelium. 

You  will  observe  prominently  some  dark  lines  (the  larger  vessels) 
traversing  the  specimen.  Select  a  thin  spot  between  the  vessels  and 
focus  H,  you  have  a  picture  like  Fig.  27.  The  field  is  traversed  by 
very  delicate  dark  lines,  indicating  the  position  of  the  cement  sub- 
stance ;  while  the  nuclei  of  the  cells  are  pink  from  the  carmine  stain- 
ing. 

With  the  fine  adjustment-screw  run  the  tube  of  the  microscope 
down  carefully.  The  cement  lines  will  disappear,  and  before  they 
are  completely  out  of  focus,  another  set  of  cells  will  appear  below  the 
first  set.  So  you  may  alternately  bring  into  view  the  upper  and  under 
layers  of  cells  covering  the  respective  sides  of  the  mesentery. 

Observe  the  irregular  shape  of  the  cells.  Note,  also,  that  the  cells 
on  one  side  average  larger  than  those  on  the  other  side.  You  may 
also  notice  in  various  parts  of  the  specimen  blood-vessels  lined  with 
cells  which  are  outlined  with  the  silver  staining. 

Sketch  a  field  showing  the  elements  as  in  Fig.  27,  £nd  stain  the 
nuclei  with  the  carmine  solution. 

COLUMN AE   CKLLS. 

Columnar  Epithelium. 

Columnar  cells  are  found,  generally,  throughout  the  alimentary  and 
respiratory  tracts.  They  also  line  the  cerebral  ventricles,  the  urinary 
and  Fallopian  tubes,  the  uterus,  etc.  This  epithelium  is  quickly  de- 
stroyed after  death  and  is  difficult  of  perfect  demonstration  except  in 
an  animal  recently  killed. 

Procure  from  the  abattoir  a  portion  of  the  small  intestine  and  bron- 
chus of  a  pig,  and  with  the  curved  scissors  snip  out  small  pieces  from 
the  mucous  surface  of  each.  Macerate  in  one-sixth  per  cent  of  chromic 
acid  for  twenty-four  hours. 


CILIATED    COLUMNAR    EPITELIUM.  45 

Place  a  piece  of  the  gut  on  a  slide  and,  after  having  added  a  drop 
of  the  acid  solution,  scrape  off  the  mucous  surface  with  a  knife  and 
remove  the  remainder  of  the  gut.  Add  a  cover-glass  and  focus  H. 
You  will  find  cells  in  various  conditions,  from  isolated  examples  to 
small  groups  like  Fig.  28. 


FIG.  28.— COLUMNAR  CELLS  FROM  SMALL  INTESTINE  OF  RABBIT. 

A.  Tapering  attached  extremity. 

B.  A  swollen  goblet  cell. 

C.  Finely  striated  free  border. 

D.  Transparent  line  of  union  between  the  striated  portion  and  the  body  of  the  cell.    X  400. 

Observe  that  the  attached  ends  of  the  cells  are  often  small  and 
pointed,  and  that  spheroidal  and  ovoidal  cells  are  frequently  wedged 
in  between  them.  Note  the -free  border  :  It  consists  of  striae,  and  is 
separated  from  the  body  of  the  cell  by  a  translucent  line.  This  ap- 
pearance is  also  that  of  the  epithelium  in  the  human  intestine. 

Ciliated   Columnar  Epithelium. 

Prepare,  by  scraping,  a  slide  from  the  mucous  surface  of  the  pig's 
bronchus  (which  has  been  macerating  in  the  chromic  acid). 

Observe  the  cilia  on  the  free  border  of  the  cells.  Interspersed  be- 
tween ciliated  cells,  much  enlarged  individuals  may  be  found,  the  so- 
called  beaker,  goblet  or  mucous  cells. 

The  motion  of  the  cilia  may  be  demonstrated  as  follows  : 

Carefully  open  an  oyster  so  as  to  preserve  the  fluid.  On  examina- 
tion you  will  notice  the  leaflets,  shown  in  Fig.  30,  commonly  called 
the  beard.  With  the  scissors  snip  off  a  fragment. of  the  free  border  of 


46  PRACTICAL    MICROSCOPY. 

this  beard,  add  a  drop  of  the  liquid  from  the  oyster,  and  tease  with  a 
pair  of  needles.     Apply  the  cover  and  focus  H. 

At  first,  the  individual  cilia  cannot  be  demonstrated  on  account  of 


Fio.  29.— CILIATED  COLUMNAR  CELLS  FROM  BRONCHUS  OF  PIG.    X  400. 

their  rapid  vibration.  After  a  few  moments,  however,  the  action  be- 
comes less  energetic,  and  the  hair-like  appendages  of  the  cells  are  to 
be  plainly  seen. 


FIG.  30.— OYSTER,  OPENED  TO  SHOW  METHOD  OF  PROCURING  LIVING  CILIATED  CELLS. 

A.  The  divided  muscle.    This  must  be  sectioned  before  the  shell  can  be  opened. 

B.  The  Heart. 

C.  Liver. 

D.  D.    The  so-called  "  beard."    These  laminae  are  covered  with  cells  provided  with  cilia  ;  and 
a  fragment  of  the  free  border  of  one  of  the  leaflets  may  be  snipped  with  the  scissors,  and 
examined  as  described  in  the  text. 

Of  course  none  of  the  above  objects  are  intended  to  be  perma- 
nent. 


BED    BLOOD-CORPUSCLES.  4T 

SPHEROIDAL   CELLS. 

The  only  cells  which  have,  in  any  very  great  number,  retained  their 
primitive  spheroidal  form  are  the  corpuscles  of  the  blood  and  of  the- 
lymphatic  system. 

In  solid  organs,  the  cells,  primarily  spheroids,  often  become  poly- 
hedral from  pressure. 

Cells,  developed  spheres,  not  unfrequently  send  out  prolongations, 
forming  either  stellate  or  polar  cells  according  to  the  size  of  the  radi- 
ating processes. 

RED   BLOOD-CORPUSCLES. 

The  human  red  blood-corpuscle  is  a  flattened,  bi-concave  disc,  one- 
three  thousand  two  hundredth  of  an  inch  in  diameter.  It  presents  a. 


FIG.  31.— CORPUSCULAR  ELEMENTS  OF  HUMAN  BLOOD. 

A.  Colored  corpuscles  adhering  by  their  sides— rouleaux. 

B.  The  same  crenated. 

C.  The  same  shrunken. 

D.  The  same  having  absorbed  water. 

E.  The  same  still  more  swollen. 

F.  The  same  with  the  plane  C  D,  Fig.  32,  in  focus. 

G.  The  same  with  the  plane  A  B,  Fig.  32,  in  focus. 
H.  Colorless  corpuscles,     x  400. 

mass  of  protoplasm  destitute,  as  far  as  the  microscope  shows,  of  nuclei,, 
cell- wall,  or  any  structure  whatsoever. 


48  PRACTICAL   MICROSCOPY. 

Certain  changes  in  form  result,  after  removal  from  the  circulation, 
yiz. :  1.  They  may  adhere  by  their  broad  surfaces  forming  columns. 
2.  From  shrinkage  they  may  become  crenated.  3.  Still  further 
shrinkage  produces  the  chestnut-burr  appearance.  4.  From  absorp- 
tion of  water  they  may  swell  irregularly,  obliterating  the  concavity  of 
one  side.  5.  From  continuous  absorption  they  swell,  forming  spheres 
which  are  finally  dissolved. 

Wind  a  twisted  handkerchief  tightly  around  the  left  ring  finger ; 


w 

FIG.  32.— DIAGRAM  OF  A  COLORED  BLOOD-CORPUSCLE,  SIDE  VIEW  SHOWING  THE  BI-CONCAVITY. 

A,  B,  Upper  plane;  which,  in  focus,  gives  the  appearance  shown  at  G,  Fig.  31. 
C,  D,  Plane  giving  the  appearance  F,  Fig.  31. 

prick  the  end  with  a  clean  needle,  and  squeeze  a  minute  drop  of  blood 
on  a  slide,  add  a  drop  of  saliva,  cover  and  focus  M. 

Observe  : — 1.  That  considerable  variation  in  size  of  the  red  blood- 
corpuscles  exists.  2.  The  color — a  delicate  straw  tint.  3.  That  the 
concave  centre  of  the  corpuscles  which  lie  flat  can  be  made  to  appear 
alternately  dark  and  light  according  to  the  focal  adjustment.  4.  That 
the  concavity  is  also  demonstrated  as  the  corpuscles  are  turned  over  by 
the  thermal  currents.* 


BLOOD-PLATES. 

Minute  corpuscular  elements  in  the  blood  about  one-fourth  the  size 
of  the  red  discs  exist  in  the  proportion  of  about  one  of  the  former  to 
twenty  of  the  latter.  They  are  colorless  ovoid  discs;  and  are  regarded 
by  Osier  as  an  essential  factor  in  the  coagulation  of  the  blood. 

Prick  the  thoroughly  clean  finger  with  a  needle.  Over  the  puncture 
place  a  drop  of  solution  of  osmic  acid  (vide  formulae)  and  squeeze  out 
a  minute  drop  of  blood  so  that,  as  it  flows,  it  is  covered  by  the  acid 
solution.  This  fixes  the  anatomical  elements,  providing  against 
further  change.  The  blood,  as  soon  as  drawn,  must,  with  the  acid,  be 

*  The  student  is  at  this  time  advised  to  study  the  corpuscular  elements  of 
the  blood  of  such  animals  as  he  may  be  able  to  command.  The  red  corpuscles 
of  mammals  (excepting  the  camelidse)  do  not  vary  in  appearance  from  those 
of  man,  excepting  in  size.  Those  of  birds,  fishes,  and  reptiles  are  elliptical 
with  oval  nuclei.  Corpuscles  of  the  blood  of  invertebrates  are  not  colored. 


POLYHEDRAL   CELLS.  49 

immediately  transferred  to  a  slide  and  covered.     To  provide  against 
evaporation,  run  a  drop  of  sweet  oil  around  the  edge  of  the  cover. 


FIG.  33.— HUMAN  BLOOD  PRESERVED  WITH  OSMIC  ACID. 

A.  Colored  corpuscles. 

B.  Colorless  corpuscle. 

C.  C,  C.    Groups  of  plaques.    X  400  and  reduced. 

The  blood-plates  may  be  found,  after  careful  search,  bearing  the 
relation  to  the  red  corpuscles  seen  in  Fig.  33. 

WHITE   OE   COLORLESS   BLOOD-CORPUSCLES. 

The  white  blood-corpuscle  is  a  typical  cell,  spherical  in  form, 
presenting  generally  a  nucleus — often  two  or  more — with  nucleolL 
In  diameter  about  the  one-twenty-five  hundredth  of  an  inch,  they  are 
usually  found  in  the  blood  in  proportion  of  one  to  three  hundred  to  one 
thousand  red  corpuscles.  The  nucleus  of  the  white  corpuscle  possesses 
nearly  the  same  refractive  index  as  the  body  of  the  cell,  and  is  there- 
fore difficult  of  demonstration  without  the  use  of  reagents  or  staining. 

Procure  a  drop  of  pus  from  a  healing  wound,  mix  it  on  a  slide  with 
an  equal  quantity  of  dilute  eosin  solution,  cover  and  examine  H. 

Pus  is  colorless,  containing  spherical  nucleated  corpuscles,  the 
perfect  ones  resembling  exactly  those  found  in  healthy  blood.  Ob- 
serve that  the  nuclei,  some  cells  containing  three  or  even  four,  are 
stained  with  the  eosin.  Minute  pigment  granules  and  fat  globules 
appear  in  many  of  the  pus  cells,  and  others  are  broken  and  distorted. 

POLYHEDRAL    CELLS. 

With  a  scalpel  scrape  the  cut  surface  of  a  piece  of  liver  from  a 
recently  killed  pig ;  place  a  minute  portion  of  the  finer  part  on  a 


50  PRACTICAL    MICROSCOPY. 

slide;  add  a  drop  of  normal   salt  solution  (vide  formulae);  mix  with 
a  needle,  and  put  on  the  cover-glass. 

With   H.    observe,   among    the     numerous    blood-corpuscles,    fat 
globules,  etc.,  the  polyhedral  liver  cells,  about  twice  or  three  times  the 


FIG.  34.— GLANDULAR  EPITHELIA. 

A,  A.    Polyhedral  cells  from  human  liver. 

B.  Double  nuclei. 

O.    Cells  from  same  showing  connection  with  a  capillary. 

D.  Same  cells  infiltrated  with  globules  of  fat. 

E.  Cells  from  liver  of  pig  showing  intracellular  net- work,    x  400 , 

diameter  of  a  white  blood-corpuscle  (Fig.  34).  Notice  the  large 
spherical  nuclei,  with  nucleoli.  Note,  also,  the  yellow  pigment  granules 
and  the  fat  globules  in  the  body  of  the  cells.  Masses  of  these  cells 
resemble  somewhat  pavement  epithelium;  they  are  not  flat  but  poly- 
hedral. 

STELLATE    CELLS. 

When  we  arrive  at  the  study  of  the  skin,  I  shall  show  you  some 
very  beautiful  examples  of  stellate  cells.  I  prefer  to  leave  their 
demonstration  until  you  have  become  more  familiar  with  tissue  cut- 
ting. 

POLAR   CELLS. 

.  As  I  have  stated,  spheroids  may  send  off  processes.  These  pro- 
longations may  be  one,  two,  three,  or  more  in  number,  constituting 
unipolar,  bipolar,  tripolar,  etc.,  cells.  The  best  demonstration  is 
made  from  the  nervous  system,  where  these  poles  are  continued  as 
nerves,  etc. 


WHITE    FIBROUS   TISSUE.  51 

From  a  freshly  slaughtered  ox,  sheep,  or  pig  (the  first  being  the 
best)  obtain  a  piece  of  the  spinal  marrow  from  the  region  of  the  neck. 
Out  it  transversely  into  discs  about  one-eighth  of  an  inch  thick,  and 
place  them  in  the  chromic-acid  fluid  diluted  with  an  equal  bulk  of 
water.  After  thirty-six  hours,  place  one  of  the  pieces  in  water,  and 
with  a  needle  pick  out  minute  fragments  from  the  anterior  horn  of 
the  gray  matter  (refer  to  the  diagram  of  the  spinal  cord)  and  trans- 
fer them  to  a  slide.  Add  a  drop  of  water  and  break  the  tissue  into 
minute  fragments  by  teasing  with  a  pair  of  needles.  Examine  from 
time  to  time  with  L.  to  note  the  progress  of  the  teasing.  When 
properly  teased,  put  on  the  cover-glass  and  search  for  large  nucleated 
cells  from  which  the  prolongations  or  horns  are  given  off.  Compare 
with  Fig.  123. 

Cells  may  be  classified  as  follows: 

Epithelial — covering-cells,  as  in  skin. 

Endothelial — lining-cells,  lining  vessels  or  cavities,      n' 

Glandular — constituting  the  parenchyma  of  organs.  \ 


CONNECTIVE   (FIBROUS)  TISSUES. 

Certain  elementary  structures  of  similar  origin  and  mode  of  de- 
velopment, and  serving  alike  to  unite  the  various  parts  of  the  body, 
have  been  termed  connective  tissues.  Custom  has  restricted  the 
term,  in  its  every-day  employment,  so  as  to  apply  to  white  fibrous 
tissue  or,  at  least,  to  tissue  which  always  resembles  this  more  closely 
than  any  other,  and  I  shall  so  use  the  expression  in  this  work. 

WHITE   FIBROUS   TISSUE. 

This,  the  connective  tissue  par  excellence,  is  composed  of  exceed- 
ingly  fine  fibrillae  (one-fifty  thousandth  of  an  inch),  which  are  aggre- 
gated in  irregularly  sized  and  variously  disposed  bundles.  It  forms 
long  and  exceedingly  strong  tendons  connecting  muscle  and  bone; 
its  fibres  interlace,  forming  the  delicate  network  of  areolar  tissue  ;  it 
forms  thin  sheets  of  protecting  and  connecting  aponeuroses;  or,  sup- 
porting vessels,  it  permeates  organs,  and  sustains  the  parenchyma  of 
glands. 

The  fibres  are  held  together  by  means  of  a  transparent  cement, 
which  may  be  softened  or  dissolved  in  acetic  acid.  They  may  exist, 
as  in  dense  tendons,  without  admixture. 

Cells  are  found  between  the  bundles  of  fibres,  known  as  connective- 
tissue  corpuscles  or  fibro-blasts.  The  older  and  more  dense  the  struc- 
ture, the  less  frequent  are  these  cells  ;  while  in  young  (recent)  con- 


52 


PRACTICAL   MICROSCOPY. 


nective  tissue,    stained,  the  nuclei  of   the   corpuscles  constitute  a 
prominent  feature  of  the  specimen  under  the  microscope. 

Having  obtained  a  piece  of  tendon  from  a  recently  killed  bullock, 
tease  a  fragment  on  a  slide  in  a  few  drops  of  water.  Select  a  portion 
which  splits  easily  and  separate  the  fibrils  as  much  as  possible. 
Cover  and  examine  H. 


FIG,  35.— CONNECTIVE  TISSUE. 

A.  Teased  fibres  from  a  tendon. 

C.  Fibrillfie. 

B.  New  connective  tissue  from  a  cirrhotic  liver. 

D.  Elongate  cells  in  last  showing  mode  of  formation  of  fibrillae  from  cell  elements,     x  400. 

Fine,  wavy  fibres  are  seen  composing  the  fasciculae.  If  the  dissec- 
tion has  been  sufficiently  minute,  you  may  succeed  in  demonstrating 
ultimate  fibrillae.  These  are  best  made  out,  as  at  0  in  Fig.  35, 
where  the  parts  of  a  bundle  have  been  separated  for  some  distance, 
leaving  the  finer  elements  stretching  across  the  interval. 

B  in  Fig.  35  shows  recently  formed  connective  tissue  from  the  liver, 
where  this  structure  had  so  increased  as  to  largely  obliterate  the 
parenchyma  of  the  organ. 

YELLOW   ELASTIC   TISSUE. 

This  tissue  consists  of  coarse  shining  fibres  (averaging  one-three 
thousandth  of  an  in.)  which  frequently  branch  and  anastomose.  They 
are  highly  elastic.  Under  the  microscope  the  fibres  are  colorless ; 
but  when  aggregated,  as  in  a  ligament,  the  mass  is  yellow. 


YELLOW    ELASTIC   TISSUE. 


53 


FIG.  36.— TEASED  YELLOW  ELASTIC  TISSUE  FROM  THE  LIQAMENTUM  NUCHJE.    X  250. 


FIG.  37.— TRANSVERSE  Sscn  >N  OF  PART  OF  THE  LIGAMENTUM  NUCH.E. 

S.    Sheath  of  the  ligament,  sanding  prolongations  within  -as  at  T  T— dividing  the  structure 
into  irregular  bundles  or  fasciculae. 
L.    Lymph  spaces  in  the  connective  tissue. 
A.    Adipose  tissue  in  the  sheath. 
V.    Blood-vessels  in  transverse  section. 
E5  E.    Primitive  fasciculae  of  yellow  elastic  tissue  fibres.     X  250. 


54  PRACTICAL   MICROSCOPY. 

Procure  a  small  piece  of  the  ligamentum  nuchce  of  the  ox,  and  tease- 
it  on  the  slide  after  its  having  been  macerated  in  acetic  acid  for  a  few 
moments.  The  acid  softens  the  fibrous  connective  tissue  and  facili- 
tates the  teasing  process. 

The  individual  fibres  having  been  isolated,  they  appear  as  in  Fig. 
36.  When  broken,  they  curl  upon  themselves  like  threads  of  India 
rubber. 

This  tissue  is  variously  disposed  throughout  the  body  where  great 
strength  with  elasticity  becomes  necessary.  The  large  arteries  are 
abundantly  supplied  with  elastic  fibre,  arranged  in  plates,  in  alterna- 
tion with  muscle.  As  a  network,  it  is  mixed  with  connective  ti>sue  in 
the  skin,  and  in  membranes  generally.  It  contributes  elasticity  to 
cartilage  where  the  fibres  form  an  intricate  network. 

Ligaments  are  composed  largely  of  yellow  elastic  tissue.  Fig.  37  is 
drawn  from  a  portion  of  a  stained,  transverse  section  of  the  ligamen- 
tum siifrflava. 

A  strong  sheath  of  fibrous  tissue  is  thrown  around  the  whole  liga- 
ment, a  portion  of  which  is  seen  at  S.  This  sheath  sends  prolonga- 
tions, T,  T.  into  the  structure,  dividing  it  into  irregular  bundles, 
which  support  nutrient  vessels.  The  elastic  fibres  seen  in  transverse 
section,  as  at  E,  E,  are  observed  strongly  bound  together  with  fibrous 
tissue,  which  penetrates  the  smaller  fasciculae,  dividing  them  into  the 
ultimate  fibr  illce. 

ADIPOSE   TISSUE. 

Adipose  or  fat  tissue  is  a  modification  of,  and  development  from 
ordinary  connective  tissue. 

It  originates  in  certain  contiguous  connective-tissue  corpuscles,  be- 
coming filled  with  minute  fat  globules.  These  ultimately  coalesce 
and  form  single,  large  globules,  which  bulge  out  the  cell-bodies  until 
they  become  spheroids  ;  the  nuclei  at  the  same  time  are  displaced  to 
the  periphery.  An  aggregation  of  such  cells  forms  a  lobule  of  adi- 
pose tissue.  The  cells  are  often  so  closely  packed  as  to  assume  a 
polyhedral  form.  From  malnutrition,  this  fat  may  be  absorbed, 
ordinary  connective  tissue  remaining. 

You  will  bear  in  mind  the  fact  that  whenever  fat  exists  in  a  condi- 
tion of  minute  subdivision,  the  particles  always  assume  the  globular 
form;  and  that  while  adipose  tissue  contains  fat,  fat  alone  is  not 
adipose  tissue. 


ADIPOSE  TISSUE. 


FIG.  38.— CONNECTIVE-TISSUE  CELLS  CONTAINING  FAT— INDICATING  THE  MODE  OF  FORMATION,  or 

ADIPOSK  TISSUE. 

A.  Ordinary  elongate  connective-tissue  cells. 

B.  Same  containing  minute  globules  of  fat. 

C.  Coalescence  of  the  fat  globules  and  displacement  of  the  nucleus. 

D.  Still  greater  increase  of  the  fat.    x  400. 


FIG.  39. — ADIPOSK  TISSUE  FROM  TEASED  HUMAN  OMENTUM    STAINED  WITH  ELEMA. 

A.  Connective-tissue  framework. 

B.  Cells  distended  with  fat  showing  fat  crystals. 

C.  Cells  from  which  the  fat  has  been  dissolved  by  ether. 

D.  Cells  faintly  seen  below  the  more  sharply  focussed  plane.    X  400. 


56 


PRACTICAL    MICROSCOPY. 


CAETILAGE. 

Cartilage  consists  of  a  dense 'basis  substance,  in  which,  cells  or  chon 
droblasts  are  imbeded.  It  presents  in  three  forms. 

HYALINE    CABTILAGE. 

The  matrix  of  hyaline  cartilage  is  transluscent,  dense,  and  appar- 
ently structureless.  Minute  channels  in  certain  instances,  and  deli 
cate  fibrillae  in  others,  have  been  demonstrated. 


Fia.  40.— SECTION  OF  HYALINE  CARTILAGE  FROM  A  HUMAN  BRONCHUS. 

The  ground  substance  is  apparently  structureless,  and  it  contains  the  membrane-lined  exca- 
vations in  which  one,  two,  three,  or  more  cartilage  cells  appear.  These  cells  show  a  well- 
marked  intra-cellular  network,  x  400. 

The  basis  material  contains  excavations,  generally  spherical,  called 
lacunce.  They  are  lined  with  a  delicate  membrane  and  contain  one, 
two,  three,  and  perhaps  as  many  as  eight  cells — the  cartilage  corpus- 
cles. 

Hyaline  cartilage  is  found  covering  joints  generally,  where  it  is 
termed  articular  cartilage.  It  is  also  found  in  the  trachea,  the 
bronchi,  the  septum  narium,  etc. 

Fig.  40  shows  a  section  from  one  of  the  rings  of  a  large  bronchus. 


FIBRO-CARTILAGR. 

Fibrous  connective  tissue  predominating  largely  in  the  basis  sub- 
stance, produces  a  structure  of  great  strength — fibro-cartilage.     The 


ELASTIC    OR    RETICULAR    CARTILAGE. 


57 


intervertebral  discs  afford  an  example  of  this  variety,  from  a  section 
of  which  Fig.  41  has  been  drawn.     The  membrane  lining  the  lacunae 


FlO.  41.— FlBRO-CARTILAGft  FROM  AN  INTERVERTEBRAL  PLATE  OR  DlSC. 

The  ground-substance,  unlike  that  of  the  hyaline  variety,  consists  of  dense  fibrous  tissue  with 
little  calcareous  matter,    x  400. 

is  much  thicker  than  in  the  previous  example,  and  the  fibrous  tissue 
is  a  very  prominent  feature  of  the  ground  substance. 


ELASTIC   OR    RETICULAR   CARTILAGE. 

As  the  name  implies,  yellow  elastic  tissue  is  an  important  element 
of  the  ground  substance  of  elastic  cartilage.     It  presents  in  the  form 


FIG  42.— ELASTIC  CARTILAGE  PROM  EAR  OF  BULLOCK. 
The  ground-substance  consists  largely  of  a  network  of  coarse,  yellow  elastic  tissue     X  400. 


58 


PRACTICAL    MICROSCOPY. 


of  a  reticulum,  as  shown  in  Fig.  42.  It  is  not  extensively  distributed 
in  the  human  being,  although  the  cartilages  of  the  external  ear,  Eusta- 
chian  tube,  etc.,  are  of  this  variety. 

Cartilage  should  be  hardened  by  the  chromic  acid  and  alcohol  pro- 
cess. The  sections  from  which  the  illustrations  have  been  drawn 
were  cut  without  the  microtome.  They  should  be  cut  extremely  thin, 
not  necessarily  large.  We  frequently  succeed  in  getting  good  fields 
from  the  thin  edges  of  sections  which  may  be  elsewhere  too  thick. 
Stain  with  haema.  and  eosin.  The  differentiation  will  be  excellent. 
The  delicate  nutritive  channels  in  the  matrix  connecting  the  lacunae 
may  be  demonstrated  in  the  cartilage  of  the  sternum  of  the  newt;  the 
xiphoid  appendix  is  sufficiently  thin  without  sectioning. 

BONE. 

Bone  consists  of  an  osseous,  lamellated  matrix,  in  which  occur 
irregularly  shaped  cavities — la>'unce.  The  latter  are  connected  by 
means  of  exceedingly  fine  channels — canaliculi.  The  lacunae  contain 


FIG.  43.— PORTION  OF  A  TRANSVERSK  SECTION  FROM  A  DRIED  FEMUR  SHOWING  PART  OF  THE  WAIJU 

OF  AN  HAVERSIAN  SYSTEM. 

A,  A.    Bony  laminee. 

B,  B,    Lacunse. 

C,  C.    Canaliculi.     X  400. 


BONE. 


59 


the  fione  corpuscles,  the  bodies  of  which  are  projected  into  the  cana- 
liculi. 

In  compact  bone,  the  blood-vessels  run  in  a  line  parallel  with  the 
long  axis  of  the  bone,  in  branching  inosculating  channels  (averaging 
one-five  hundredth  of  an  inch) — the  Haversian  canals.  The  lamellae 
of  osseous  tissue  are  arranged  concentrically  around  these  canals.  A 
single  Haversian  canal  with  the  lamellae  surrounding  and  belonging 
to  it  constitute  an  Haversian  system. 

The  lamellae  beneath  the  periosteum  are  not  arranged  as  above,  but 


FIG.  44. — TRANSVERSE  SECTION  OF  PORTION  OF  A  DRIED  LONG  BONE,  SHOWING  THE  HAVERSIAN 

SYSTEMS. 

A,  A,  A.    An  Haversian  system. 

B.  Haversian  canal. 

The  lacunae,  canaliculi,  and  Haversian  canals  all  appear  black  in  the  section,  as  they  are  filled 
with  air  and  the  bony  fragments  resulting  from  grinding  of  the  section,     x  60. 

parallel  with  the  surface  of  the  bone.     These  plates  are  perforated  at 
right  angles,  and  obliquely  by  bloo>l- vessels  from  the  periosteum,  as 
they  pass  on  their  way  to  the  Haversian  canals.     These  lamellae  are 
also  perforated  by  calcific  connective  tissue — the  perforating  fibres  of 
Sharpcy. 

An  Haversian  canal  contains  (Fig.  44)  an  artery,  a  venule,  lymph 


60  PRACTICAL    MICROSCOPY. 

channels,  and  a  nerve  filament.  The  whole  is  supported  by  connective- 
tissue  cells  with  delicate  processes.  The  walls  of  the  lymph  spaces  are 
prolonged  into  the  caualiculi  and  thus  placed  in  connection  with  the 
elements  of  the  surrounding  lacunae. 


FIG.  45.— DIAGRAM  OF  AN  HAVERSIAN  CANAL. 

A.  Artery. 

B.  Vein. 

C.  Nerve. 

D.  D,  D.    Lymph-channels. 


Each  lacuna  contains  a  bone  corpuscle,  the  protoplasmic  body  of 
which  sends  prolongations  into  the  contiguous  canaliculi.  In  the  adult 
bone,  the  cell  is  shrunken  ;  and  the  processes  just  mentioned  are  not 
readily  demonstrable. 


FIG.  46.  -  DIAGRAM  OF  A  BONE  LACUNA. 

A,  A.    Ground-substance  of  the  bone. 

B,  B.     Limiting  membrane  of  the  bone  corpuscle  within  the  lacuna. 

C,  Nucleus  and  nucleolus  of  the  corpuscle. 

D,  D.    Projection  of  the  cell-body  into  the  canaliculi. 

" 

Fig.  44  has  been  drawn  from  a  section  of  dry  bone  which  has  been 
sawn  as  thin  as  possible,  and  afterward  rubbed  down  on  a  hone  with 
water.  It  is  a  tedious  process,  and  shows  little  but  the  osseous  ma- 
trix. Bone  should  be  decalcified  for  microscopical  work,  and  it  may 


SPECIAL   CONNECTIVE    TISSUES.  61 

then  be  readily  cut  in  thin  sections  with  a  razor.  The  process  is  as 
follows; 

To  four  ounces  of  the  dilute  chromic-acid  solution  add  a  drachm  of 
0.  P.  nitric  acid.  The  bone,  previously  divided  into  slices  not  over 
one-fourth  cf  an  inch  in  thickness,  is  then  placed  in  the  fluid,  and 
should  be  completely  decalcified  in  a  week  or  ten  days.  Examine  the 
pieces  after  twenty-four  hours  by  puncturing  with  a  needle.  Should 
the  action  proceed  too  slowly,  add  a  few  drops  more  of  the  nitric  acid 
from  time  to  time.  The  bone  eventually  takes  on  a  green  color. 
After  complete  decalcification,  wash  the  pieces  for  twenty-four  hours 
in  clean  water,  and  preserve  them  until  required,  in  "  B  "  alcohol. 
Small  pieces  of  young  bone  may  be  decalcified  in  a  saturated  aqueous 
solution  of  picric  acid.  The  process  is  slow,  but  it  leaves  the  tissue 
in  excellent  condition. 

Sections  cut  in  the  usual  way  may  be  stained  with  carmine  and 
picric  acid,  and  examined  in  a  drop  of  glycerin.  They  should  not 
after  the  staining  be  placed  in  the  oil  of  cloves,  as  they  would  curl  and 
become  hard.  Transfer  them  to  equal  parts  of  glycerin  and  water, 
from  which  they  are  to  be  carried  to  the  slide.  Add  a  drop  more  of 
the  dilute  glycerin  if  necessary  and  put  on  the  cover-glass,  carefully 
avoiding  air  bubbles.  If  you  desire  to  make  a  permanent  mounting, 
the  edge  of  the  cover  must  be  cemented  to  the  slide. 

Thoroughly  wipe  the  slide,  around  the  cover,  with  moistened 
paper,  until  every  trace  of  glycerin  is  removed.  Then  with  a  sable 
brush,  paint  a  ring  of  zinc  cement  (vide  formulas)  around  the  slide 
just  touching  the  edge  of  the  cover-glass.  Repeat  the  cementing  in 
twenty-four  hours.  A  turn-table  will  be  a  useful  aid  in  this  work. 
Dr  Carl  Heitzmann,  who  uses  glycerin  as  a  universal  mounting  fluid, 
prefers  ordinary  black  (asphalt)  varnish  as  a  cement. 


SPECIAL   CONNECTIVE  TISSUES. 

Connective  Tissue  of  the  Lymphatic  System. — The  matrix  of  lym- 
phoid  or  adenoid  tissue  consists  of  a  network  of  branching  cells, 
which  support  the  lymph  corpuscles.  It  is  distributed  extensively 
in  organs,  and  where  it  appears  in  stained  sections,  the  lymphoid 
cells  are  so  numerous  as  to  obscure  the  reticulum  almost  entirely.  The 
structure  will  be  minutely  described  in  connection  with  the  lym- 
phatic system. 

The  Connective  Tissue  of  the  Central  Nervous  System  (neuroglia) 
consists  of  branched  connective-tissue  cells,  which  are  supported  in 


62 


PRACTICAL     MICRO-SCOFF. 


3-n  intimate  network  of  exceedingly  fine  elastic  fibrillae,    and  will  re- 
ceive attention  later  in  our  work. 

Embryonic  Connective  Tissue  presents  a  homogeneous,  mucoid 
matrix  containing  branched  cells.  It  is  not  found  normally  in  the 
adult. 

MUSCULAR   TISSUE. 

This  tissue  is  found  in  three  varieties:  1.  Non-striated  or  involun- 
tary; 2.  Striated,  red,  skeletal,  or  voluntary;  3.  Cardiac. 

N02ST- STRIATED   MUSCLE. 

The  histological  element  of  non-striated  muscle  is  a  spindle-shaped 
cell  from  one-tenth  to  one-five  hundredth  of  an  inch  long.  The  cell 
body  presents  longitudinal  striae,  and  contains  an  ovoid  nucleus.  The 
nucleus  contains  a  reticulum  which  is  probably  in  connection  with  the 


FIG.  47.— WALL  OF  THE  FROG'S  BLADDER,  STAINED  WITH 

A.  A.    Bands  of  involuntary  muscular  fibre,  recognized  by  the  spindle-cell  sarcous  elements. 

B.  A  small  arteriole,  showing  the  same  muscular  element. 

C.  Scattering  muscle  cells. 

D.  Connective  tissue  cells.    X  400. 


fibrillae,  which  produce  the  longitudinal  striation  of  the  body.  The 
cells  are  not  unfrequently  bifid  at  one  or  both  extremities.  A  trans- 
parent cement  substance  serves  to  unite  these  cells  in  forming,  with 
connective  tissue,  broad  membranous  plates,  bundles,  plexuses,  etc. 


STRIATED    MUSCULAR   TISSUE.  DO 

It  serves  to  afford  contractility,  especially  to  the  organs  of  vegetative 
life. 

Kill  a  good-sized  frog  by  decapitation,  and  open  the  abdomen  on 
the  median  line.  Fill  the  bladder  with  air,  after  the  introduction  of 
a  blowpipe  into  the  vent.  Remove  the  inflated  bladder  with  a  single 
cut  with  the  curved  scissors,  and  place  it  in  a  saucer  of  water.  Pro- 
ceed to  brush  it,  under  the  water,  with  two  earners  hair  pencils  so  as 
to  remove  all  of  the  cells  from  the  inner  surface.  It  will  bear  vigor- 
ous rubbing  with  one  of  the  brushes,  holding  it  at  the  same  time  with 
the  other.  Transfer  to  alcohol  for  ten  minutes,  and  afterward  stain 
with  haema.  and  eosin.  While  in  the  oil,  cut  the  tissue  into  small 
pieces,  and  mount  flat  in  dammar.  Examine  L.  and  H. 

Observe  the  bands  of  involuntary  muscle  crossing  in  various  direc- 
tions. You  will  distinguish  (Fig.  47)  between  the  muscle  and  the 
connective  tissue  cells  by  their  nuclei. 

STRIATED   MUSCULAR   TISSUE. 

A  skeletal  or  striated  muscle  consists  of  cylindrical  fibres,  one-three 
hundredth  to  one-six  hundredth  of  an  inch  in  diameter,  and  one  to 
two  inches  long.  These  primitive  fibres  are  supported  by  a  delicate, 


FIG.  48.— DIAGRAM  INDICATING  THE  MINUTE  STRUCTURE  OF  STRIATED  MUSCULAR  FIBRE. 

A,  A.    Sarcolemma. 

B,  Krause's  line  connecting  with  the  sarcolemma  and  dividing  the  fibril  into  compartments. 

C,  C.    The  rod-like  contractile  substance. 

D ,  Hensen's  middle  disc. 


64  PRACTICAL     MICROSCOPY. 

transparent  sheath — the  sarcolemma.  They  are  aggregated,  forming 
primitire  fasciculi,  which  are  again  united  to  form  the  larger  bundles 
of  a  complete  muscle.  The  connective  tissue  uniting  the  primitive 
fibres  is  termed  endomysium  ;  while  that  uniting  the  primitive  bun- 
dles is  the  perimysium. 

The  primitive  muscular  fibres  exhibit  marked  cross  striations  with 


FIG.  49.— STRIATED  MUSCULAR  FIBRES  PROM  THE  TONGUE,  TEASED  AND  STAINED  WITH 

A.  A  fibre,  with  the  muscle  substance  wanting,  from  stretching  during  the  teasing,  the  sar- 
colemma alone  remaining. 

B.  Partly  separated  disc  of  Bowman. 

C.  Ultimate  fibrillae. 

D.  A  blood  capillary.     X  400. 

faint  longitudinal  markings,  the  former  being  produced  by  alternate 
dark  and  light  spaces. 

Fig.  48  illustrates  diagrammatically  the  theory  of  the  structure  of 
a  primitive  fibre:  A  indicates  the  sarcolemma.  The  dark  substance 
B,  B  (Krause's  membrane)  divides  the  fibre  completely,  and  is  united 
with  the  sarcolemma.  The  light  spaces  C,  C,  between  Krause's 
membranes,  containing  the  contractile  substance,  are  termed  the 
muscular  compartments  or  discs  of  Bowman.  This  contractile  sub- 


CARDIAC    MUSCULAR    FIBRE. 


65 


stance  in  the  living  muscle  is  semi-fluid,  but  in  hardened  tissue  it 
can  be  split  up,  as  indicated  at  0,  into  rods,  the  sarcous  elements.  A 
transparent  line,  D,  in  this  contractile  substance  can  sometimes  be 
demonstrated;  it  is  known  as  Hensen's  middle  disc. 

Macerate  human  muscle,  preferably  that  from  the  tongue,  in  dilute 
chromic  acid  for  twenty-four  hours;  wash,  tease  in  water,  cover  and 
focus  H.  Fig.  49  was  drawn  from  such  a  preparation. 

The  sarcolernma  is  best  seen  where  the  contractile  substance  has 
been  broken.  The  muscle  nuclei  are  seen  at  various  points  beneath 
the  sarcolemma.  Portions  of  a  fibre  have  been  split  off  transversely 
in  places,  indicating  the  discs  of  Bowman.  Sarcous  elements  are  in- 
dicated where  the  fibre  has  been  split  during  the  teasing.  The 
capillaries  are  arranged  in  a  direction  parallel  to  the  fibres,  with  fre- 
quent transverse  connections. 

CARDIAC    MUSCULAR   FIBRE. 

It  presents  the  following  characteristics: 

1.  The  fibres  are  smaller  than  those  of  ordinary  skeletal  muscle, 

2.  They  are  striated  both  transversely  and  longitudinally, 

3.  They  branch,  forming  frequent  inosculations. 


FIG.  50.— TEASED  CARDIAC  MUSCULAR  FIBRE. 
Stained  with  heema.    X  400  and  reduced. 


4.  They  are  divided  by  distinct  transverse  lines  into  short  prisms. 

5.  Their  nuclei  are  situated  within  the  fibre. 

6.  They  present  no  distinct  sarcolemma. 

5 


66  PRACTICAL    MICROSCOPY. 

Fig.  50  has  been  drawn  from  fresh  cardiac  muscle,  teased  in  nor- 
mal salt  solution,  and  tinted  with  eosin. 

BLOOD-VESSELS. 

Blood-vessels  include  arteries,  arterioles,  capillaries,  venules, 
and  veins.  They  are  all  lined  with  flattened  endothelial  cells 
cemented  by  their  edges;  and  their  walls  are  constructed  from  non- 
striated  muscular,  yellow  elastic  and  fibrous  connective  tissues,  in 
proportions  varying  according  to  the  size  and  function  of  the  vessel. 
Arteries  are  the  active,  while  the  veins  are  comparatively  passive 
agents  in  the  circulation  of  the  blood. 

The  large  arteries  are  eminently  elastic,  from  preponderance  of  yel- 
low elastic  tissue;  while  the  arcerioles  are  eminently  contractile,  from 
excess  of  muscular  fibre. 


FIG.  51.— TRANSVERSE  SECTION  OF  A  MEDIUM-SIZED  ARTERY,  PARTLY  DIAGRAMMATIC. 

A.  The  endothelial  cells  in  profile. 

B.  Elastic  and  connective  tissue  supporting  the  endothelium. 

C.  The  internal  elastic  lamina  or  fenestrated  membrane.    A,  B,  and  C  constitute  the  INTIMA 
of  the  artery. 

D.  The  MEDIA.    It  consists  of  muscular  and  elastic  tissues  in  alternating  layers. 

E.  Points  to  one  of  the  elastic  layers. 

F.  The  ADVENTITIA.    Loose,  connective  tissue,  with  few  elastic  fibres. 

Arteries  possess  three  coats:  the  intima  (internal),  media  (middle), 
and  adventilia  (external). 

Fig.  51  represents  a  medium-sized  typical  artery.  The  intima,  or 
internal  coat  (1),  consists  of  a  layer  of  flattened  endothelial  cells, 
which  rest  upon  fibrous  connective  tissue,  with  a  few  elastic  fibres. 
The  last  is  surrounded  by  a  layer  of  elastic  tissue,  the  elastic  lamina 
or  fenestrated  membrane,  which  is  the  external  limit  of  the  intima. 
It  presents  in  a  transverse  section  as  a  wavy  (from  contraction  of 


BLOOD-VESSELS.  O7 

the  media)  shining  line;  and  is  an  important  element,  from  its  rela- 
tion to  certain  abnormalities  of  the  blood-vessels.  The  media  (2) 
consists  of  alternate  layers  of  elastic  and  muscular  tissue.  The  ad- 
ventitia  (3)  is  composed  of  fibrous  connective  tissue,  containing  some 
elastic  elements. 

As  we  approach  the  larger  arteries,  the  muscular  tissue  diminishes 
in  quantity  and  the  elastic  tissue  is  increased.  On  the  other  hand, 
the  elastic  element  diminishes  with  preponderance  of  muscle  as  we 
approach  the  smaller  arteries,  until  we  meet  the  arterioles,  the  walls 
of  which  are  made  almost  exclusively  of  involuntary  muscular  fibre. 

The  walls  of  capillaries  consist  of  a  single  layer  of  flattened  endo- 
thelial  cells  cemented  by  their  edges.  The  union  is  not  quite  con- 


FIG.  52.— ISOLATED  BLOOD  CAPILLARIES. 

A.  Plexus  from  a  pulmonary  alveolus,  stained  with  ssilver.     X  350. 

B.  Capillary  from  omentum,  stained  with  silver  and  hsema.     X  700. 

In  A,  the  cells  are  outlined  by  the  silver;  while  in  B  the  nuclei  in  addition  are  brought  out  by 
the  haema. 

tinuous,  as  minute  openings  (stomata)  are  to  be  seen  at  irregular  in- 
tervals. 

The  walls  of  veins  are  much  thinner  than  those  of  arteries.  The 
intima  presents  an  endothelial  lining,  but  no  fenestrated  membrane; 
and  the  line  of  demarcation  between  this  coat  and  the  media  is  often 
indistinct.  The  media  contains  muscular,  but  little  elastic  tissue; 
and  the  adventitia,  usually  the  most  prominent  of  the  three  coats,  is 
composed  largely  of  fibrous  connective  tissue. 

I  shall  defer  the  microscopical  examination  of  blood-vessels  until 
we  meet  them  in  future  sections  of  organs,  as  they  are  best  studied 
in  such  connection. 


PART   THIRD. 


ORGANS. 


THE    SKIN". 

The  skin  consists  of  (1)  the  epidermis  (or  scarf  skin),  which  every- 
where covers  and  protects  (2)  the  derma  (corium  or  true  skin). 

The  epidermis  varies  greatly  in  thickness  in  different  locations; 
and  in  the  thicker  portions  several  layers  may  be  differentiated.  It 
is  composed  entirely  of  cells,  while  the  derma  is  fibrous. 


Stratum  Gorneum,  \  H          L  ,  | 

/Stratum  Luciaum,  } 

Stratum  Granulosum  }  Malpighian  Layer  \  I 

Stratum  of  Prickle  Cells,  \      W  ,|  Muoomim 

5.  Stratum  of  Elongate  (Pigment)  Cells,  )  °  <J  S 


The  stratum  corneum  consists  of  old.  exhausted,  flattened,  and 
desiccated  cells,  which  are  constantly  falling  from  the  entire  surface 
of  the  body.  Dandruff  consists  of  impacted  cells  from  this  source. 
Those  portions  most  frequently  exposed  to  friction,  e.  g.,  the  palms 
of  the  hands  and  soles  of  the  feet,  are  protected  by  a  corneous  epider- 
mal layer  of  great  thickness. 

The  stratum  lucidum,  or  clear  layer,  presents  cells  in  form  not 
unlike  those  in  the  preceding  stratum;  they  are,  however,  translucent. 
This  is  properly  a  part  of  the  previous  stratum,  is  often  absent,  and 
frequently  very  difficult  of  demonstration. 

:    The  stratum  granulosum,  or  granular  layer,  is  composed  of  flat- 
tened cells  containing  opaque  granules. 


THE    SKIN. 


69 


Immediately  beneath  the  last-named  layer,  the  cells  become  strik- 
ingly altered  in  form  and  appearance.  The  prickle  cells  are  poly- 
gons or  compressed  spheroids,  with  large,  oval  nuclei,  and  minute, 
projecting  spines.  By  means  of  these  processes  they  are  very  firmly 
united. 

The  fifth  and  last  (deepest)  layer  of  the  epidermis  is  composed  of 
a  single  rank  of  elongate  cells,  placed  with  their  long  axes  at  right 
angles  to  the  surface  of  the  skin.  These  cells  contain  the  pigment 
which  gives  the  hue  peculiar  to  the  skin  of  colored  individuals. 


FIG.  53. — VERTICAL  SECTION  OP  THE  EPIDERMIS  FROM  THE  PALM  OF  THE  HAND.    Stained  with 

Hasina,  and  Eosin. 

A.  Stratum  corneum. 

B.  Stratum  lucidum. 

C.  Stratum  granulosum. 

D.  Prickle  cells  of  rete  mucosum  or  R.  Malpighii. 

E.  Stratum  of  elongate  cells,  the  lower  limit  of  the  epidermis. 

F.  F.    Indicate  the  position  of  two  papillee  of  the  true  skin  or  derma.     X  400. 


The  first  two  layers  of  the  epidermis  constitute,  properly,  the 
horny  layer;  while  the  remaining  three  strata  compose  the  rete  mu- 
cosum or  rete  Malpighii. 

The  derma,  corium,  or  true  skin  is  composed  of  dense,  fibrillated 
connective  tissue,  so  formed  as  to  present  minute  elevations  or  papil- 


70  PRACTICAL     MICROSCOPY. 

lae  over  the  entire  surface  of  the  body.  These  papillae  are  covered 
with  a  basement  membrane,  and  are  protected  from  undue  irritation 
by  the  epidermal  layers. 

The  subcutaneous  cellular  tissue  (upon  which  the  true  skin  rests) 
consists  of  fibrillated  connective-tissue  with  elastic  elements,  from 
which  strong  interlacing  bands  are  formed.  These,  in  the  deeper 
parts,  form  septa  which  support  lobules  of  adipose  tissue.  These  iso- 
lated collections  of  adipose  tissue,  when  elongated  and  placed  verti- 
cally to  the  surface,  constitute  the  fat  columns  of  Satterthwaite. 


FIG.  54.— VERTICAL  SECTION  OF  THE  DERMA,  OR  TRUE  SKIN. 

A,  A.    Line  of  elongate  cells  belonging  to  the  epidermis. 

B,  B,  B.    Summits  of  three  papillae  of  the  true  skin. 

C,  C,  C.    Portions  of  capillary  loops  in  the  papillae. 

D,  D.    Nerve  loops,  tactile  corpuscles.     X  250. 

The  blood-vessels  supplying  the  skin  may  be  seen  in  vertical  sec- 
tions, in  the  subcutaneous  tissue.  Branches  from,  these  are  sent  to 
the  papillae,  where  they  terminate  in  delicate,  interlacing  loops  of 
capillaries. 

Medullated  nerves  are  also  sent  to  the  papillae  ;  and  in  certain  lo- 
ations,  they  may  be  seen  to  terminate  in  tortuous  structures — the 


THE    HAIES.  71 

tactile  corpuscles.     Varicose  nerve  fibrils  have  been  traced  between 
the  cells  in  the  rete  mucosum  of  the  epidermis. 

APPENDAGES   OF  THE   SKIN. 

The    appendages  of  the   skin   are   the    hairs,    sebaceous  glands, 
sudoriferous  glands,  and  the  nails. 


THE   HAIRS. 

A  hair,  consisting  of  a  root  and  shaft,  is  constructed  from  elongate 
cells  which  are  cemented  together,  and  overlapped  with  cell-plates. 
The  central  part  of  medullated  hairs  is  composed  of  cubical  cells,  pig- 
ment, and  occasional  minute  air  bubbles. 

The  root  penetrates  the  stratum  corneum  and  (appearing  to  have 
pushed  the  rete  mucosum  before  it)  passes  through  the  true  skin  and 
terminates  in  a  bulb  usually  in  the  subcutaneous  tissue,  where  it 


Fia.  55. — TRANSVERSE  SECTION  OF  HAIR,  AND  HAIR-FOLLICLE.    Partly  Diagrammatic. 

A.  Meiulla  of  hair.  . 

B.  Cortex  of  same. 

C.  Root  Sheath. 

D.  Glassy  membrane. 

E.  Fibrous  wall  of  the  follicle, 

rests  upon  a  papilla  composed  of  an  extremely  delicate  plexus  of 
blood  capillaries. 

The  Hair  Follicle. — The  root  of  the  hair,  in  its  passage  to  the 
papilla,  is  invested  with  sheaths  derived  from  the  skin.  The  hair, 
with  its  follicle,  is  indicated  in  transverse  section  in  Fig.  55.  A 
represents  the  medulla,  and  B  the  cortex  of  the  hair.  Outside  the 
root  sheath  C,  and  derived  from  the  rete  mucosum  of  the  epidermis, 
is  a  thin  layer,  the  glassy  membrane  D.  This  is  projected  from  the 
basement  membrane  covering  the  surface  of  the  corium  or  true  skin. 


PRACTICAL    MICROSCOPY. 


The  whole  is  surrounded  by  a  fibrous  coat  E,  derived  from  the  con- 
nective tissue  of  the  derma. 

A  vertical  section  of  the  follicle  is  indicated  in  Fig.  56.     A,  B,  and 
C  represent  the  epidermal  layers  which  do  not  enter  into  its  composi- 


FIG.  56.— DIAGRAM  SHOWING  MODE  OF  FORMATION  OF  HAIR-FOLLICLE. 
A'.    Epidermal  layers. 
B'.    Derma  or  true  skin. 

A.  Horny  layer  of  epidermis. 

B.  Stratum  lucidum. 

C.  Stratum  granulosum. 

The  three  last-mentioned  form  no  part  of  the  follicle. 

D.  Rete  Malpighii.    This  will  be  seen  projected  into  the  depths  of  the  true  skin  to  form  the 
root-sheath  G. 

E.  Hyaline  membrane  covering  the  derma.    This  is  projected  into  the  follicle,  forming  the 
glassy  membrane,  G. 

F.  Fibrous  tissue  of  the  derma,  forming  the  fibrous  sheath  of  the  hair-f ollicle,  I. 

G.  Root-sheath  of  the  hair-follicle. 
H.    Glassy  membrane  of  the  follicle. 
I.    Fibrous  sheath  of  the  follicle. 

J.    The  hair-follicle. 

tion.  The  rete  mucosum  D  forms  the  root-sheath  at  Gr.  The  base- 
ment membrane  of  the  corium  E  forms  the  glassy  membrane  H, 
while  the  connective  tissue' F  constitutes  the  fibrous  layer  of  the  hair 
follicle  J. 


SUDORIFEROUS    GLANDS. 

A  sweat  gland  consists  of  a  tube  or  duct  (vide  Fig.  57,  at  A) 
which,  from  the  opening  upon  the  surface,  passes  in  a  spiral  course 
through  the  several  layers  of  the  skin  to  the  deeper  part  of  the 
corium,  where  it  becomes  coiled  in  a  bunch  as  at  D.  The  coiled  or 
gland  part  of  the  tube  is  surrounded  by  a  network  of  capillaries.  At 
B,  the  tube  is  seen  in  transverse  section.  The  gland  tube  D  is  pro- 
vided with  a  wall  of  connective  tissue  and  smooth  or  involuntary 
muscle,  lined  with  conical  cells.  The  epithelial  lining  of  the  duct  C 
is  granular;  the  lumen  small  and  lined  with  a  thin  cuticular  mem- 


SUDORIFEROUS    AND    SEBACEOUS    GLANDS. 


73 


FIG.  57.— SUDORIFEROUS  TUBULAR  GLAND. 

A,  Diagrammatic  sweat-gland.    C.    Its  duct.    D.    Coiled,  glandular  part. 

B.  The  same,  showing  a  transverse  section  of  both  parts,    x  400.    C'.    The  duct  lined  with 
several  layers  of  cells.    D'.    The  coiled  glandular  part  lined  with  columnar  cells  in  a  single 
layer. 


A. 
B. 
C. 
D. 

X400. 


FIG.  58. — SINGLE  LOBULE  OF  A  SEBACEOUS  GLAND. 
The  fibrous  wall  of  the  sac. 
Involuntary  muscular  element  of  the  wall. 
Polyhedral  cells  filling  rhe  sac  completely. 
Fatty  degeneration  of  the  parenchyma  at  the  neck  of  the  gland,  formation  of  sebum. 


74  PRACTICAL    MICROSCOPY. 

brane.  The  latter  constitutes  the  entire  wall  of  the  duct  as  the  sur- 
face of  the  epidermis  is  approached,  the  cellular  elements  having  dis- 
appeared. 

Krause  estimated  the  number  of  sweat  glands  at  over  two  millions. 

SEBACEOUS  GLANDS. 

These  glands  are  -little  sacs  or  lobules,  one  or  more  of  which  open 
into  each  hair  follicle.  These  sacs  are  entirely  filled  with  polyhedral 
cells  (vide  Fig.  58).  At  the  neck  of  the  gland  the  cells  become 
granular,  fatty,  and  disintegrated,  producing  the  sebum. 

MUSCLES    OF   THE   HAIE    FOLLICLES. 

Attached  to  the  fibrous  layer  of  each  hair  follicle  is  a  small  band 
of  involuntary  or  smootli  muscular  fibre — the  arrector  pili.  This 
passes  obliquely  toward  the  surface  of  the  skin;  and  when  contrac- 
tion takes  place,  the  follicle  and  hair  are  elevated,  producing  the 
phenomenon  known  as  goose-flesh. 

PKACTICAL  DEMONSTRATION. 

Remove  the  skin  from  the  parts  below  as  soon  after  death  as  prac- 
ticable. Tissue  may  frequently  be  secured  after  surgical  operations 
from  stumps,  etc.  Dissect  deeply  so  as  to  preserve  the  subcutaneous 
tissue.  Small  cubes  from  the  finger-tips,  the  palm  of  the  hand,  the 
scalp,  and  the  groin  may  be  hardened  quickly  in  strong  alcohol  ;  and 
vertical  sections  should  be  made  as  soon  as  the  tissue  has  become  suf- 
ficiently firm.  Stain  with  ha3ma.  and  eosin,  and  mount  in  dammar. 

The  structure  of  hairs  may  be  best  demonstrated  by  washing  the 
soap  from  lather,  after  shaving,  with  several  changes  of  water. 
When  clean,  decant  the  water  and  add  alcohol.  After  twenty-four 
hours  again  decant  and  add  oil  of  cloves.  With  a,  pipette  carry  a 
drop  of  the  oil  with  the  deposited  hair  cuttings  to  a  slide,  remove  as 
much  of  the  oil  as  possible  with  slips  of  blotting-paper,  and  mount 
in  dammar.  Oblique,  vertical,  and  transverse  sections  may  be  readily 
obtained  by  this  method. 

VERTICAL   SECTION   OF   SKIN    FROM   THE   GROIN. 

(Vide  Fig.  59.) 
OBSERVE  : 

(L.)* 

1.  The  horny  layer  of  the  epidermis.  (The  stratum  lucidum 
will  hardly  be  demonstrable  on  account  of  the  thinness  of  the  epider- 
mis in  this  region.) 

*  Low  power,  i.  e.,  from  thirty  to  sixty  diameters. 


VERTICAL    SECTION    OF    SKIN    FROM   THE   GROIN. 


75 


2.  The  rete  mucosum.     (The  section  from  which  the  illustration 
has  been  drawn  was  taken  from  a  negro,  and  the  deep  cells  were  pig- 
mented.) 

3.  The  sharp  line  of  demarcation  between  the  epidermis 
and  the  true  skin. 


FIG.  59. — VERTICAL  SECTION  OF  SKIN  PROM  THE  GROIN.    Stained  with  Hsema.  and  Eosin. 

A.  Epidermis. 

B.  Deep,  elongated  cells  of  the  rete  mucosum. 

C.  C.    Papillae  of  true  skin. 

D.  D.    Subcutaneous  areolar  tissue. 

E.  E.    Collections  of  adipose  tissue. 

F.  Shaft  of  hair  (obliquely  sectioned). 

G.  Root-sheath  of  last. 
H.    Fibrous  sheath  of  last. 

I.    Hair  papilla  (vertical  section^. 

J,  J,  J.    Portions  of  sebaceous  glands  (one  on  the  extreme  right  of  the  cut  is  seen  in  connec- 
tion with  the  hair-follicle). 
K,  K.    Arrectores  pili. 

L.    Hair-follicle  with  contained  shaft  of  hair  in  very  oblique  section. 
M,  M.    Coils  of  sudoriferous  glands. 
N.    Spiral  duct  of  last. 
O,  O.    Arteries  of  subcutaneous  plane. 


4.  The  papillae  of  the  corium  or  derma.     (Note  the  absence  of 
any  sharp  line  dividing  the  corium  and  subcutaneous  tissues). 

5.  The   larger    blood-vessels    of  the     subcutaneous     region. 


76  PRACTICAL    MICROSCOPY. 

(The  arteries  in  transverse  section  are  plainly  indicated  by  their 
prominent  media,  the  appearance  of  the  fenestrated  membrane  as  a 
wavy  yellowish  line,  and  by  the  elliptical  or  circular  outline.  The 
veins  are  smaller,  with  thinner  walls,  and  their  outline  is  generally 
irregular.  The  smaller  veins  are  commonly  overlooked,  on  account 
of  their  lumen  having  become  obliterated  by  contraction  of  the  tissue 
in  hardening.) 

6.  Coils    and    ducts  of  sweat   glands  in   last  region.     (The 
tubes  are  cut  in  various  directions,  and  the  whole  is  surrounded  by 
dense  fibrous  tissue,  forming  a  kind  of  capsule.) 

7.  The  collections  of  adipose  tissue  beneath  the  last  region. 
(The  septa  are  dense  and  strong.) 

8.  (Having  selected  a  vertical  section  of  a  hair  follicle:)  (a)  The 
root  of  the  contained  hair,     (b)  The   bulb  and  the  hair  pa- 
pilla,    (c)  The  medulla  of  the  hair,     (d)  The  root-sheath  pro- 
longed from  the  rete  mucosum.     (e)  The  fibrous  (outer)  sheath. 

9.  The  sebaceous  glands.     (The  demonstration  of  the  connection 
between  the  neck  of  the  gland  and  the   follicle  will  require  a  very 
favorable  section.) 

10.  (Scattered  through  thecorium  and  upper  subcutaneous  region:) 
(a)  Small  portions  of  sebaceous  glands,     (b)  Ducts  of  sudor- 
iferous glands,     (c)  Oblique  sections  at  various  angles  of  hair 
follicles     (d)  Small  vessels. 

11.  Arrector  pili  muscle.     (Nearly  always  to  be  found  standing 
obliquely  to  the  divided  hair  follicle. ) 

(H.)* 

12.  (If  demonstrable  :)  (a)  The  stratum  lucidum.     (b)  Stratum 
granulosum. 

13.  The  elongate  cells  of  the  rete,  next  the  corium. 

14.  (Where  the  tissue  has  been  torn  :)  The  impacted  cells  of  the 
horny  epidermis. 

15.  The  basement  membrane  covering  the  corium. 

16.  Capillaries  of  the  papillae  of  the  corium.     (These  may  be 
distinguished,  when  seen  longitudinally,  by  tortuous  lines  of  elongate 
and  deeply  stained  nuclei  belonging  to  the  endothelium.     Arterioles 
may  be  differentiated  by  their  long  muscle   cells,  the  circular  fibres 
lying  transversely  to  the  vessel. ) 

17.  The  root-sheath  of  the  hair  follicles.     (The  cells  composing 
the  root-sheath  vary  in  appearance,  according  to  their  position  rela- 

*  Hign  power,  i.  e.,  from  three  to  four  hundred  diameters. 


VERTICAL    SECTION   OF    SKIN    FROM    THE    GROIN.  77 

tively  to  the  hair  ;  and  this  will  enable  you  to  demonstrate  two  layers, 
or  an  inner  and  an  outer  root-sheath.) 

18  The  glassy  membrane  of  the  hair  follicle.  (Appearing 
simply  as  a  clear  space  between  the  root-sheaths  and  the  outer  fibrous 
coat. ) 

19.  The  intra-cellular  network  in  the  large  polyhedral  cells  of 
the  sebaceous  glands,  and  the  minute  fat  globules  in  the  same. 

20.  The  nuclei  of  the  fat  cells  in  the  adipose  tissue.     (They  ap- 
pear pressed  to  one  side). 

21.  Medullated  nerve  bundles  in  transverse  or  oblique  section. 


78  PRACTICAL    MICROSCOPY. 


THE    TEETH. 

A  human  dentinal  tooth  is  a  calcific  structure  of  extreme  hardness, 
and  is  divided  into  an  exposed  crown,  a  constricted  neck,  and  one  or 
more  concealed  fangs — the  latter  being  inserted  into  an  alveolus,  by 
means  of  which  the  whole  is  firmly  connected  with  the  maxilla. 

The  central  portion  presents  an  elongate  cavity  (pulp -chamber) 
containing  vascular,  nervous,  and  connective-tissue  elements — the 
pulp. 

The  pulp-cavity  is  surrounded  by  the  dentine,  which  constitutes 
the  major  portion  of  the  tooth. 

The  crown  portion  of  the  dentine  is  provided  with  a  covering  of 
enamel,  while  the  fang  is  invested  with  an  osseous  cement,  the  crusta 
petrosa. 

A  thin  (one-twenty  five  thousandth  to  one-fifty  thousandth  of  an 
inch)  membrane — the  cuticula — covers  the  enamel  in  early  life, 
while  the  crusta  receives  a  periostea!  investiture.  The  vascular  and 
nervous  elements  of  the  pulp  obtain  admission  to  the  pulp-cavity  by 
a  perforation  or  foramen  at  the  apex  of  the  fang,  the  foramen  den- 
tium. 

The  Pulp. — The  ground-substance,  or  stroma  of  the  pulp,  is  a  form 
of  primitive  connective  tissue,  gelatinous  rather  than  markedly 
fibrous.  It  contains  elongate  capillary  loops,  multipolar  cells,  me- 
dullated  and  non-medullated  terminal  nerve  fibrils. 

Surrounding  the  pulp  mass,  and  next  to  the  dentinal  wall  of  the 
chamber,  we  find  a  single  layer  of  elongate  cells — odontoblasts.  These 
are  in  communication,  by  means  of  processes,  or  prolongations,  with 
fibrous  elements  of  the  pulp. 

Dentine. — The  dentinal  stroma  or  matrix  is  cartilaginous,  with 
calcific  elements,  and  is,  next  to  the  enamel,  the  hardest  tissue  of  the 
body.  The  matrix  is  pierced  with  the  dentinal  canals  (one-ten  thou- 
sandth to  one-twenty  thousandth  of  an  inch  in  diameter)  which  radiate 
from  their  beginning,  next  the  pulp-chamber,  toward  the  outer  por- 
tion of  the  dentine.  These  canals  branch  and  anastomose,  and  are 
lined  with  an  exceedingly  thin  dentinal  sheath. 

From  the  outer  extremity  of  the  odontoblasts  of  the  pulp  numer- 
ous prolongations  are  sent  which  are  continued  within  the  dentinal 
canals  as  the  dentinal  fibres.  The  dentinal  canals  terminate  exteriorly, 
by  very  fine  lumina,  in  a  system  of  irregularly  formed  openings,  in- 
ter globular  spaces,  which  are  channeled  in  the  outer  part  of  the  den- 


THE   TEETH. 


79 


tine.     The  dentirial  terminal  fibres  are  in  connection  with  branched 
cells  which  occupy  the  interglobular  spaces. 


FIG.  60. -VERTICAL  SECTION  OF  BICUSPID  TOOTH.    DIAGRAMMATIC. 

A,  A.    Pulp  chamber. 

B,  Foramen  dentium  for  entrance  of  vascular  and  nervous  elements  to  the  pulp. 

C,  C,  C.    Dentine.    The  lines  point  to  the  incremental  lines  of  Salter,  imperfectly  calcified 
dentinal  stroma. 

D,  D.    Interglobular  spaces  in  last  layer,  forming  the  granular  layer  of  Purkinje. 

E,  E.    Crusta  petrosa  or  cement  substance. 

F,  Enamel.    The  parallel  lines  are  intended  to  indicate  the  stripes  of  Retzius  due  to  the  for- 
mation of  the  enamal  in  successive  layers. 

G,  The  cuticula. 

The  Enamel. — The  part  of  the  dentine  above  the  neck  of  the  tooth 
is  protected  by  a  covering  of  enamel.  The  enamel  consists  of  prisms 
from  one-six  thousandth  to  one-eight  thousandth  of  an  inch  in  diameter 


80  PRACTICAL    MICROSCOPY. 

which  pass  in  a  direction  nearly  at  right  angles  to  the  surface  of  the 
dentine.  They  are  of  extreme  density,  contain  little  beside  inorganic 
material  and  in  a  vertical  section  the  whole  is  traversed  by  parallel 
striae,  not  unlike  the  markings  indicating  tree-growth — the  lines  of 
Retzius. 

Crusta  Petrosa. — The  fang  portion  of  the  dentine  is  invested  with 
a  thin  layer  of  true  bone,  arranged  in  laminae,  and  containing  lacunm 
and  caiialiculi,  but  no  Haversian  canals.  The  crusta  is  provided  with 
periosteum,  which  forms  the  bond  of  union  between  the  teeth  and  the 
process  of  the  maxillae.  The  lacunar  bone  corpuscles  are  in  connec- 
tion, through  the  canaliculi,  with  the  cells  in  the  interglobular  spaces 
of  the  dentine.  It  will  be  seen  that  the  connective-tissue  elements, 
at  least  of  the  pulp,  are  in  eventual  histological  connection  with  the 
bone  corpuscles  of  the  crusta. 

PRACTICAL   DEMONSTRATION. 

The  illustrations  common  to  our  text-books  have  been  drawn  from 
dried  teeth,  ground  down  to  the  requisite  thinness  by  means  of  corun- 
dum or  emery  wheels.  This  is  a  very  tedious  process,  and  is  impracti- 
cable with  the  student.  If  such  specimens  are  desired  it  will  be  ad- 
visable to  purchase  them  already  mounted.  They  only  give  the 
skeleton  of  the  organ,  all  the  soft  tissues  being  destroyed  by  the  drying 
and  grinding. 

While  dry  specimens  exhibit  the  plan  of  a  tooth,  the  soft  tissues 
must  be  studied  in  sections  made  after  the  inorganic  constituents  have 
been  removed.  Teeth  immediately  after  extraction  are  to  be  treated 
in  the  same  manner  as  described  for  bone.  A  une-sixth  per  cent  of 
chromic-acid  solution,  to  which  five  drops  of  nitric  or  hydrochloric 
acid  have  been  added,  may  be  first  used.  Let  the  quantity  of  liquid 
be  liberal,  and  from  time  to  time,  say  every  three  days,  add  a 
few  drops  of  the  nitric  acid.  The  decalcification  should  proceed 
slowly  and  may  be  complete  in  from  two  to  three  or  four  weeks.  The 
earthy  matters  will  first  be  dissolved  from  the  surface.  Watch  the 
action  carefully,  ascertaining  the  progress  of  decalcification  by  prick- 
ing a  fang  with  the  needle.  If  the  acid  be  too  strong,  and  the  action 
too  rapid,  the  whole  may  be  destroyed.  When  the  decalcification  is 
complete,  a  needle  may  be  easily  passed  through  the  tooth  and  sections 
be  made  with  the  razor  or  knife,  with  or  without  a  microtome.  The 
form  will  be  preserved  except  as  regards  the  enamel;  this  will  be  en- 
tirely dissolved.  The  enamel  prisms  may  be  demonstrated  by  treat- 
ing broken  fragments  with  dilute  acid  for  a  short  time  only. 

Sections  should  be  stained  with  carmine  and  picric  acid  and 
mounted  in  glycerin.  For  the  study  of  the  development  of  teeth, 
foetal  jaws  may  be  treated  as  just  described;  and,  when  properly  de- 
cnlcified  and  hardened,  should  be  infiltrated  with  celloidin,  sectioned 
and  stained.  I  would  refer  the  student  to  the  excellent  article  on  the 
subject  in  Dr.  C.  Heitzmann's  "Morphology." 


TEETH. PRACTICAL    DEMONSTRATION. 


81 


TKANSVERSE   SECTION   OF  FANG   OF  HUMAN  DECIDU- 
OUS  CANINE   TOOTH.-DECALCIFIED. 

(Fig.  61.) 
OBSERVE: 

(L.) 

1.  Division  into  pulp,   dentine,  crusta  petrosa,  and  perios- 
teum. 

2.  Line  of  junction  of  pulp  and  dentine.     (If  the  elements  of  the 
pulp  are  intact,  note  the  layer  of  deeply  stained  odontoblasts  next 
.the  dentine. 


FIG.  61.— TRANSVERSE  SECTION  OF  FANG  OF  A  DECIDUOUS  CANINE  TOOTH,  DECALCIFIED  WITH 
CHROMIC  AND  NITRIC  ACIDS,  AND  STAINED  WITH  PICRO-CARMINE. 

A,  B.  Line  through  the  dentine  indicating  the  point  at  which  the  edges  have  been  made  to 
join  after  the  omission  of  an  intervening  portion.  This  was  necessary  in  order  that  the  different 
layers  might  be  shown  in  a  single  drawing. 

C,  D     Junction  line  between  the  pulp  and  dentine. 

E,  F.    Junction  line  between  dentine  and  crusta  petrosa. 

G,  G.    Odontoblasts  of  the  pulp. 

H,  H.    Stellate  connective-tissue  cells  of  the  pulp. 

I,  I.    Dentinal  processes  of  odontoblasts. 

J,  J.    Dentinal  fibres. 

K,  K.    Terminal,  branching,  dentinal  fibres. 

L,  L     Interglobular  spaces  of  dentine. 

M,  M.  Lacunae  of  the  crusta  petrosa.  The  drawing  does  not  show  the  periosteal  investiture 
of  the  crusta.  X  400. 

6 


82  PRACTICAL   MICROSCOPY. 

3.  External   limit  of  dentine.     (Note   here  the  deeply  stained 
granular  line  of  Purkinje.     This  is  the  location  of  the  interglobular 
spaces.     The  deep  color  is  due  to  the  staining  of  their  cell  contents.) 

4.  The  striae  of  the  dentine   (dentinal  canals  and  stained  con- 
tents). 

5.  The   laminated  crusta.     (The   yellowish  pink   dots  on    the 
lacunae.) 

(H.) 

6.  Elements  of  the  pulp,     (a)  The  layer  of  odontoblasts  (note 
their  internal  processes  connecting  with  other  cells  of  the  pulp;  and 
the  external  processes  passing  into  the  dentinal  canals).     (b)  The 
sparsely  fibrillated  character  of  the  pulp  tissue,     (c)  Sections  of 
vascular  loops.     (The  nerve  elements  may  be  demonstrated,  par- 
ticularly if  the  section  be  made  near  the  apex  of  the  fang,  where  the 
fibres  are  medullated.     The  terminal  fibrillse  are  non-medullated.) 

7.  Dentinal    elements,      (a)  The  dentinal   canals,      (b)  The 
dentinal  sheath.     (Better  demonstrated  in  transverse  sections.)  (c) 
Dentinal   fibres.     (In  transverse  sections  the  canals  are  well  shown 
lined  with  a  membrane  of  extraordinary  tenuity,  with  the  fibre  appear- 
ing as  a  central  dot.)     (d)  Fine  dentinal  fibres  near  the  outer  limit* 
(e)  Interglobular   spaces.     (An  occasional  cell  may  be  made  out 
in  the  larger  spaces.     They  were  formerly  supposed  to  contain  a  gelat- 
inous  material  only.     Note  the  connection  between  these  spaces  and 
the  termini  of  the  dentinal  fibres.) 

8.  The   Crusta   Petrosa.     (a)    Its  laminated  formation,     (b) 
The  lacunae,    (c)  Bone  corpuscles  in  the  last.    (The  canaliculi  are 
not   well  demonstrated   here,  as  the  tissue   is  very  translucent  and 
feebly  stained.     These  minute   canals  are  better  indicated  in  dried 
bone. 

9.  The  periosteum.     Note  its  dense  fibrillar  mesh  work. 


THE     STOMACH.  83 


THE    STOMACH    AND    INTESTINES. 

The  stomach  and  intestines  are  lined  with  mucous  membrane,  i.  e.f 
a  membrane  containing  glands  which  secrete  mucus. 

The  gastric  and  intestinal  mucous  membranes  are  constructed  as 
follows: 

1.  The  epithelial  lining. 

2.  The  mucosa. 

3.  The  muscularis  mucoscv. 

4.  The  submucosa. 

5.  The  muscular  walls  proper. 

6.  The  fibrous  or  peritoneal  investment. 

In  descriptive  anatomy,  the  first  four  of  the  above  are  included  in 
the  mucous  coat. 

The  epithelium  of  the  inner  surface  of  that  portion  of  the  alimen- 
tary tract  under  consideration  is  of  the  columnar  variety.  Variations 
occur  in  the  deeper  layers,  which  will  be  referred  to  later  on. 

The  mucosa,  with  its  epithelial  covering,  is  thrown  into  coarse  folds, 
rugce  or  valve-like  reduplications,  which  greatly  increase  the  extent  of 
surface.  It  contains  the  principal  glands  and  capillary  blood-ves- 
sels.* 

The  muscularis  mucosse  is  a  thin  layer  of  involuntary  muscular 
fibre  which  separates  the  mucosa  from  the  submucosa. 

The  submucosa,  composed  of  loose  areolar  tissue,  serves  to  connect 
the  previous  structures  with  the  muscular  coat  proper,  and  contains 
the  larger  trunks  from  which  the  capillaries  of  the  mucosa  either  take 
their  origin,  or  into  which  they  empty.  An  intricate  plexus  of  lym- 
phatics is  also  here  situated. 

The  muscular  coat  consists  of  strong  bands,  running  in  two  or  three 
directions.  The  muscle  plates  are  sustained  by  connective  tissue. 

A  peritoneal  investment  covers  the  organs,  except  at  such  points  as 
are  occupied  by  the  entrance  and  exit  of  blood-vessels,  etc. 

THE    STOMACH. 

The  mucosa  everywhere  contains  microscopical  depressions,  the  gas- 
tric tubules  or  peptic  glands.  These  are  concerned  in  the  production 
of  the  gastric  juice,  and  in  the  absorption  of  fluids. 

*  It  is  not  always  possible  in  mucous  membranes  to  differentiate  clearly  be- 
tween an  epithelial  lining  and  the  mucosa;  and  in  the  stomach  and  intestine 
they  may  be  both  included  in  the  mucosa. 


04  PRACTICAL    MICROSCOPY. 

The  several  layers  of  the  stomach  may  be  better  understood  by  ref- 
erence to  the  diagram  (Fig.  62). 

The  gastric  tubular  glands  are  of  two  principal  varieties,  viz. :  1, 
The  peptic  glands,  found  in  the  cardiac  portion  of  the  stomach;  2, 
The  pyloric  glands,  which  occupy  the  pyloric  extremit}7"  of  the  organ. 
The  mucous  membiane,  midway  between  the  cardiac  and  pyloric  por- 
tions, is  occupied  by  tubules  which  partake  of  the  character  of  both 
peptic  and  pyloric  glands,  so  that  no  sharp  boundary  line  exists. 

The  peptic  or  cardiac  gland-tubes  penetrate  to  the  muscularis  mu- 


FIG.  62.— DIAGRAM  OF  THE  WALL  OF  THE  STOMACH  IN  VERTICAL  SECTION. 

A.  Layer  of  gastric  tubules. 

B.  Vascular  portion  of  mucosa. 

C.  Muscularis  mucosae. 

D.  Submucosa. 

E.  Internal  circular  layer  of  muscular  fibre. 

F.  External  oblique  and  longitudinal  muscular  layers. 

G.  Peritoneum. 

I,  I,  I.    Lumen  of  gastric  tubules. 
J,  J.    Branching  gastric  tubules. 

K,  K.    Blood-vessels  arising  from  lower  portion  of  mucosa,  forming  plexus  'between  the 
tubules. 


cosae.  They  pursue  a  somewhat  wavy  course,  and  at  their  lower  or 
blind  extremity  are  frequently  bifid.  They  are  lined  at  their  com- 
mencement on  the  surface  with  translucent  columnar  epithelium,  the 
cells  being  polygonal  in  transverse  section.  As  the  fundus  or  bottom 
of  the  tube  is  approached,  the  lining  cells  become  granular,  larger, 


THE     STOMACH. 


85 


and  somewhat  polyhedral.  Next  the  wall  .of  the  tube,  large,  granular, 
bulging  cells  are  scattered  irregularly.  The  epithelium  occupies  the 
major  portion  of  the  space  in  the  tube,  so  that  the  lumen  is  very 
small. 

A  single  bifid  tube  is  represented  in  Fig.  63.  The  prominent  dis- 
tinguishing feature  of  the  peptic  or  cardiac  tubules  is  afforded  by  the 
large  border  or  parietal  cells.  The  cells  next  the  lumina  are  called 
central  or  chief  cells. 

The  pyloric  gland-tubes  pursue  a  course  not  greatly  unlike  that  of 
the  tubes  just  mentioned.  They  do  not  branch,  however,  until  they 
have  penetrated  well  down  toward  the  muscularis  mucosae.  Their 
distinguishing  character  is  afforded  by  the  epithelial  lining.  At  the 


FIG.  63.— VERTICAL  SECTION  OP  A  PEPTIC  TUBULAR  GLAND,  FROM  CARDIAC  MUCOSA  OF  STOMACH, 
LARGELY  DIAGRAMMATIC. 

A.  Lumen  of  duct-portion  of  tubule. 

B.  Neck  of  last. 

C.  Gland  portion. 

D.  D.    Central  cells. 

E.  E.    Border  cells. 

F.  The  glandular  portion  in  T.  S. 

G.  Line  of  commencing  muscularis  mucosae. 

surface,  the  cells  are  columnar  with  polygonal  transection.  The 
deeper  parts  are  lined  with  translucent  cylinders.  The  lumina  are 
larger  than  those  of  the  peptic  tubes. 

The  gastric  gland-tubes  are  placed  thickly  side  by  side,  their  bases 
reaching  the  muscularis  mucosae.  Between  and  beneath  the  tubes  is 
a  dense  network  of  blood  capillaries. 


86  PRACTICAL   MICROSCOPY. 

The  remainder  of  the  stomach  has  little  special  interest  for  the 
histologist.  The  muscular  portion  of  its  walls  consists  of  a  thin 
internal  circular  layer,  with  oblique  bundles  interspersed,  and  a  thin 


FIG.  64.— VERTICAL  SECTION  OF  TORTUOUS  AND   BRANCHING  TUBULAR  GLAND,  FROM  PYLORIC 
MUCOSA  OF  STOMACH.    DIAGRAMMATIC. 

A.  Lumen.    This  is  often  much  widened. 

B.  Duct  portion  of  tubule. 

C.  Branching  glandular  portion. 

D.  Transverse  section  of  the  last. 

E.  Lower  limit  of  mucosa. 

external  longitudinal  layer  of  the  involuntary  variety.  Between  the 
two  layers  is  found  a  plexus  of  non-medullated  nerves,  corresponding 
to  the  plexus  of  Auerbach  of  the  intestines,  but  which  is  not  demon- 
strable by  ordinary  methods  or  sections. 

The  blood  supply  is  received  at  the  curvatures.  Branches  pene- 
trate the  muscular  layers  along  the  lines  of  omental  attachment,  as 
blood-vessels  never  penetrate  the  peritoneum. 

The  peritoneum  is  constructed  mainly  of  fibrous  tissue,  with  an 
external  investment/ of  pavement  epithelium. 

PKACTICAL   DEMONSTKATION. 

Inasmuch  as  the  human  stomach  cannot  often  be  obtained  until 
decomposition  has  destroyed  it  for  our  work,  we  must  secure  the 
organ  from  some  one  of  the  lower  animals.  The  stomach  of  the  dog 
presents  all  the  histologies!  features  of  that  of  man,  and  can  be  gotten 
in  good  condition  from  an  animal  recently  killed. 


STOMACH. PRACTICAL    DEMONSTRATION. 


87 


Harden  small  pieces  in  strong  alcohol,  and  cut  sections  at  right 
angles  to  the  surface  and  from  different  regions. 

Stain  with  haema.  and  eosin,  and  mount  in  dammar. 

VERTICAL   SECTION  FROM    GREATER    CURVATURE   OF 
DOG'S   STOMACH. 

(Fig.  65.) 
OBSERVE: 

(L.) 

1.  The  division  into:  (a)  Surface  epithelium  (free  ends  of  gland- 
tubes),     (b)  Mucosa.    (c)  Muscularis  mucosse.    (d)  Submucosa. 


FIG.  65.— VERTICAL  SECTION  OF  WALL  OF  CENTRAL  PORTION  OF  DOG'S  STOMACH. 

A.  Internal  surface,  showing  open  mouths  of  the  gastric  tubules,  lined  with  clear  columnar 
cells. 

B.  Deepest  portion  of  submucosa. 

C.  Muscularis  mucosae. 

D.  Submucosa. 

E.  Adipose  tissue  in  last. 

F.  Bundles  of  muscular  tissue  (internal  circular),     x  60. 

(e)  Muscular  layers.     (Only  a  portion  of  the  inner  circular  layer 
is  shown.     It  has  been  divided  transversely.) 


88  PRACTICAL    MICROSCOPY. 

(H.) 

2.  The  epithelium  of  gland-tubes.     (The  upper  portion  of  the 
tubes  will  be  cut  obliquely  in  many  places,  as  they  may  have   been 
inclined,  and  the  epithelium  will  show  as  a  beautiful  mosaic  of  poly- 
gonal areas.)     (a)  The  differentiation  between  border  and  central 
cells,     (b)  Tubes  cut  transversely,  showing  the  lumina.     (c)  Indi- 
cations of  the  capillary  plexuses  between  the  tubes. 

3.  The  mucosa.     (a)  Arterioles  and   venules  beneath  the  tu- 
bules,    (b)  Scattered  lymphoid  cells  (round  cells  with  one,  two,  or 
three  nuclei). 

4.  The  muscularis  mucosae.     (Note  the  elongated  nuclei  of  the 
smooth  muscle  cells.) 

5.  The  submucosa.     (a)  Arteries,  veins,  etc.,  cut  in  various 
directions,     (b)  The  adipose  tissue.     (Crystals  of  the  fatty  acids 
are  frequently  seen  in  the  cells  when  freshly  mounted.) 

6.  The  muscular  bundles  of  the  circular  layer  with  the  septa  of 
connective  tissue.     (Note  particularly  the  various  appearances  pre- 
sented by  bundles  of  involuntary  muscular  fibre  when  cut  in  different 
planes.) 

SMALL    INTESTINE. 

The  histology  of  the  intestine,  both  large  and  small,  is  formed  upon 
the  general  plan  of  that  of  the  stomach.  The  same  layers  are  pre- 
sented: the  mucosa,  with  its  epithelial  covering;  the  muscularis 
mucosce;  the  submucosa;  the  muscular  and  the  peritoneal  coats. 

The  mucosa  of  the  small  intestine  is  everywhere  pierced  by  blind 
depressions;  or,  what  is  equivalent,  the  surface  is  studded  with 
minute  elevations  or  papillae,  between  which  are  the  depressions  which 
correspond  to  the  tubules  of  the  stomach.  The  elevations  are  called 
villi  9  the  depressions  between  the  villi,  crypts. 

The  small  intestine  serves  two  important  functions:  1,  The  secre- 
tion of  a  fluid,  one  of  the  digestive  juices — the  succus  entericus.  2, 
The  absorption  of  food,  especially  the  fats  or  hydrocarbons. 

We  shall  view  the  histology  of  this  organ  from  a  physiological 
standpoint,  considering:  1st,  Those  structures  concerned  in  the  secre- 
tion of  the  succus  entericus;  2d,  Those  portions  concerned  in  absorp- 
tion of  food. 

HISTOLOGY    OF    THOSE    PARTS    OF    THE    SMALL    INTESTINE    PARTICU- 
LARLY   CONCERNED    IN    THE    PRODUCTION  -OF    THE    SUCCUS 
ENTERICUS. 

The  diagram  (Fig.  66)  is  intended  to  represent  at  A  the  thickness 
of  the  mucosa  with  its  papillary  elevations — the  villi.  The  muscu- 


THE    SMALL    INTESTINE.  89 

laris  mucosae  B,  from  which  the  villi  arise,  separates  the  mucosa  from 
the  submucosa  C.  The  horizontal  line  at  the  bottom  of  the  diagram 
indicates  the  outer  limit  of  C  and  the  beginning  of  the  circular  mus- 
cular coat  of  the  intestine.  The  villi,  everywhere  covered  with 
columnar  epithelium,  are  represented  in  the  drawing  as  widely  sepa- 
rated, but  in  the  gut  they  are  so  closely  studded  as  to  afford  but  nar- 
row chinks  (crypts)  between  the  prominences.  In  the  interior  of 
each  villus  is  a  fine  network  of  Uood  capillaries  (G  G).  The  cells  on 
the  borders  of  the  villi  secrete  certain  fluid  material  from  the  blood 
circulating  in  the  capillary  plexuses,  and  pour  it  out  into  the  crypts. 
The  crypts  becoming  filled  with  the  fluid,  the  latter  overflows  and 
passes  into  the  lumen  of  the  gut,  to  act  in  promoting  digestion* 
This  is  one  source  of  the  succus  entericus,  and  there'is  yet  another. 


D-- 


FIG.  66.— DIAGRAM  SHOWING  PORTIONS  OF  INTESTINAL  Mucous  MEMBRANE,  CONCERNED  IN  THE 
SECRETION  OF  THE  Succus  ENTERICUS. 

A.  The  mucosa. 

B.  Muscularis  mucosse. 

C.  Submucosa. 

D.  D,  D.    Villi. 

E.  F.    Crypts  of  Lieberkuhn. 

G,  G.  G.    Blood  plexuses  of  villi. 

H,  K.    Large  vessels  of  submucosa,  supplying  the  epithelium  covering  the  villi. 

I.    Neck  of  a  gland  of  Brunner. 

J,  J,  J.    Gland  of  Brunner  in  the  submucosa.  The  secretion  is  emptied  into  the  crypts  as  at  F. 


From  the  bottom  of  some  of  the  crypts,  tubes  will  be  found  which, 
piercing  the  muscularis  mucosse,  reach  the  submucosa  where  they 
branch,  become  convoluted,  are  lined  with  secreting  cells,  and  are 
known  as  the  glands  of  Brunner.  These  glands,  which  are  practi- 
cally elongated  crypts,  are  surrounded  by  blood  capillaries,  and  the 
gland-cells  secrete  a  fluid  which  is  poured  into  the  gut  at  the  base  of 


90 


PRACTICAL   MICROSCOPY. 


the.  crypts,  when  it  becomes  mingled  with  the  secretion  previously 
mentioned,  and  constitutes  the  succus  entericus. 

We  have  then  seen  that  the  succus  entericus  is  secreted,  partly 
from  the  epithelial  cells  covering  the  villi  (or,  in  other  words,  sur- 
rounding the  crypts)  and  partly  from  Ihe  cells  of  B  runner's  glands. 

THE      REMAINING      STRUCTURES     OF      THE      INTESTINE      CONCERNED 
MAINLY    IN    FOOD    ABSORPTION. 

The  diagram  (Fig.  67)  is  intended  to  show  the  same  layers  as  were 
indicated  in  the  previous  figure  (Brunner's  glands  and  the  blood-ves- 
sels have  been  omitted  in  order  to  avoid  confusion).  The  villi  and 
crypts  are  seen  as  before. 


FIG.  67.— DIAGRAM  SHOWING  PORTIONS  OF  INTESTINAL  Mucous  MEMBRANE,  CONCERNED  IN 

ABSORPTION. 

A.  Mucosa. 

B.  Muscularis  mucosae. 

C.  Submucosa. 

D.  D.    Villi. 

E.  F.    Crypts  of  Lieberkiihn. 
G,  G.    Lacteals. 

H,  H.    Chinks  and  intercommunicating  channels  of  the  lymph  plexus  of  the  submucosa. 
I.    Bottom  of  a  mass  of  adenoid  tissue— a  so-called  solitary  gland.    Peyer's  patches  are 
formed  of  aggregations  of  these  nodules. 
J.    Efferent  lactial  or  lymph  duct. 

In  the  centre  of  each  villus  is  the  blind  tube  Gr  Gr,  a  part  of  the 
lymphatic  system,  and  here  called  a  lacteal.  When,  during  digestion, 
the  minute  globules  of  fatty  food  reach  the  small  intestine,  they  are 
grasped  by  the  epithelial  cells  covering  the  villi,  and  are  carried  event- 
ually within  the  body  of  the  villus  to  this  lacteal. 


THE    INTESTINES.  91 

The  lacteals  pierce  the  muscularis  mucosae,  and  in  the  submS^cosa 
are  in  connection  with  a  plexus  of  lymphatic  tubes  and  spaces. 
eventually  unite  with  efferent  lymph  tubes  (J),  and  pass  by  means  ol 
the  mesentery  to  the  receptaculum  chyli. 

Connected  with  the  plexus  of  lymphatics  in  the  submucosa  are 
minute  nodules  of  lymphoid  structure  (adenoid  tissue),  which  have 
unfortunately  been  called  lymphatic  glands.  They  are  in  no  sense 
glands.  , 

Slit  up  a  portion  of  intestine  along  the  attached  border,  and  care- 
fully examine  the  inner  surface:  it  will  present  a  velvety  appearance, 
due  to  the  minute  villi.  You  will  also  find  little  nodules,  perhaps 
one-sixteenth  of  an  inch  in  diameter,  scattered  here  and  there  in  the 
mucous  coat.  These  are  the  lymphatic  nodules  alluded  to  above — 
the  so-called  solitary  glands.  One  of  the  nodules  is  indicated  in  the 
diagram  at  I,  with  its  point  projecting  into  the  crypt  F. 

Continuing  your  examination  of  the  gut,  you  will  discover,  espe- 
cially in  the  ileum,  roughened  patches  perhaps  two  inches  long  by 
half  an  inch  broad.  These  are  collections  of  the  lymphatic  nodules 
described  in  the  last  paragraph,  and  are  termed  agminate  glands  or 
patches  of  Peyer.  They  have  no  secretive  power,  being  simply  in  con- 
nection with,  and  a  part  of,  the  chain  of  lymphatics  in  the  walls 
of  the  intestine.  They  consist  of  adenoid  tissue,  which  will  be  de- 
scribed with  the  lymphatics. 

To  recapitulate,  the  small  intestine  presents  the  following: 

1.  The  villi,  each  containing  a  plexus  of  blood  capillaries  and  the 
lymphatic  or  absorbent  vessel. 

2.  Crypts  or  follicles  of  Lieberkuhn,  which  are  simply  depressions 
between  the  villi. 

3.  Brunner's  glands,  the  only  true  glands  of  the  gut,  unless  the 
crypts  are  so  classified. 

4.  Solitary  lymphatic  nodules,  the  so-called  solitary  glands. 

5.  Agminate  lymphatic  nodes,  agminate  glands  or  patches  of  Peyer, 
consisting  of  aggregations  of  solitary  lymphatic  nodules. 

The  muscular  part  of  the  intestine  is  arranged  not  unlike  that  por- 
tion of  the  stomach,  i.  e.,  with  an  inner  circular  and  an  outer  longi- 
tudinal layer.  Between  the  two  is  located  Auerbach's  plexus  of  non- 
medullated  nerves.  A  similar  plexus,  Meissner's,  is  found  in  the  sub- 
mucosa. These  we  shall  not  attempt  to  demonstrate. 

A  small  quantity  of  areolar  tissue  connects  the  external  longitudi- 
nal muscular  layer  with  the  peritoneal  investment. 


y^  PRACTICAL    MICROSCOPY. 

PRACTICAL   DEMONSTRATION. 

The  intestines  of  the  dog  or  rabbit  are  more  commonly  used  for 
practical  work,  for  reasons  already  alluded  to.  The  tissue  should  be 
cut  in  small  pieces,  and  hardened  quickly  in  alcohol.  When  human, 
intestine  can  be  obtained  fresh,  a  piece,  say  three  inches  long,  should 
be  emptied  of  its  contents,  filled  with  alcohol  by  tying  the  ends,  and 
the  whole  hardened  in  strong  spirit.  Under  no  circumstances  should 
the  gut  be  washed,  and  great  care  must  be  taken  to  avoid  injuring  the 
delicate  cells  covering  the  villi.  Vertical  sections  with  the  micro- 
tome are  the  most  valuable.  Stain  with  haema.  and  eosin,  and  mount 
permanently  in  dammar. 

VERTICAL  SECTION  OF   THE  ILEUM,   INCLUDING   POR- 
TION  OF   A  PATCH   OF  PEYER.     HUMAN. 

(Vide  Fig.  68.) 
OBSERVE: 

(L.) 

1.  The  villi.  (a)  That  they  are  of  varying  lengths,  slender, 
wavy,  and  delicate,  (b)  The  covering  of  columnar  cells.  (The 


FIG.  68.— INTESTINAL  Mucous  MEMBRANE  THROUGH  A  PEYER'S  PATCH,  VERTICAL  SECTION. 
Stained  with  Haema.  and  Eosin.    X  250. 

A,  A,  A.    Villi. 

B.  Transverse  sections  of  crypts  of  Lieberkiihn. 

C,  C.    Crypts  in  vertical  section. 

D,  D,  D.    Nodules  of  lymphoid  tissue— constituting  a  patch  of  Peyer. 

E.  Muscularis  mucos®. 

F.  Submucosa. 


THE    ILEUM. PKACTICAL    DEMONSTRATION.  93 

free  extremities  of  many  of  the  villi  in  the  drawing  are  seen  broken, 
and  the  epithelium  is  wanting  in  places.  It  is  almost  impossible  to 
secure  perfect  villi  from  human  intestine,  on  account  of  the  length  of 
time  usually  intervening  between  death  and  the  removal  of  the 
tissue.)  (c)  Oblique  sections. 

2.  The  crypts  of  Lieberkuhn. 

3.  The  lymphatic  nodules  (so-called  solitary  glands),  constituting 
the  elements  of  a  patch  of  Peyer.     (a)  Their  projection  upon  the 
mucous  surface  of  the  gut  between  the  villi.     (b)  The  cover- 
ing with   epithelium   on  their  free   borders.     (They  are  located, 
properly  speaking,  in  the  submucosa  and  between  the  villi.     In  the 
drawing,  their  bases  do  not  all  appear  in  the  submucosa,  inasmuch  as 
the  nodules  are  cut  in  different  planes.) 

4.  Muscularis  mucosse.     (a)  The  elongate  nuclei  of  the  invol- 
untary muscular  element. 

5.  The    submucosa.    (a)    The      blood-vessels,      (b)    Lymph 
spaces.     (Lymphatic  channels  are  very  irregular  in  form  and  size, 
and  are  often  mistaken,  in  sections,  for  ruptures  in  the  connective 
tissue.     The  stained  nuclei  of  the  endothelial  cells,  with  which  all 
lymph  channels   are   lined,  will   enable   you   to    differentiate.)     (c) 
Glands  of  Brunner.     (There  are  none  shown  in  this  section.     The 
glands  consist  of  convoluted,  branching  tubes  which  penetrate  from 
the  crypts  to  the  submucosa.     They  are  lined  with  columnar  epithe- 
lium, and  as  they  are  divided  in  a  section,  they  resemble  very  nearly 
a  crypt  of  Lieberkuhn.     Extensive  groups  are  found  in  the  duodenum 
at  its  pyloric  origin.) 

(H.) 

6.  The  villi.     (a)  The  covering  columnar    cells,     (b)  Beaker 
cells  scattered  between  the  last.     (These  beaker,  goblet,  or  mucous 
cells  are  well  shown  in  the  intestine  of  the  dog  or  rabbit.)     (c)  The 
lacteals.     (These  are  not  plainly  demonstrable,  under  ordinary  cir- 
cumstances, in  human  tissue.     Sections  from  the  gut  of  a  dog  killed 
during  the  active  digestion  of  materials  rich  in  hydrocarbons,  will 
show  them  filled  with  minute  fat  globules. )     '(d)  The  basis  tissue, 
a  fibrous  reticulum  containing  many  lymphoid  cells,     (e)  Portions 
of  the  capillary  plexuses. 

7.  Blood-vessels  of  the  mucosa  below  the  villi. 

8.  The  adenoid  tissue  of  the  lymph  nodules. 


PRACTICAL    MICROSCOPY. 


THE    LUNG. 

BRONCHIAL    TUBES. 

At  the  root  of  each  lung  the  large  primary  bronchus  enters,  and 
immediately  divides  into  two  equal  branches — dichotomously.  It  is 
evident  that  if  this  mode  of  subdivision  were  continued,  the  peri- 


FIG.  69.— DIAGRAM  SHOWING  THE  PLAN  OF  SUBDIVISION  OF  BRONCHI,  IN  THE  HUMAN  LUNG. 

As  the  main  bronchus  enters  the  organ  it  is  seen  to  divide,  dichotomously,  until  the  resultant 
branches  become  quite  small— say  one-tenth  inch.  These  small  bronchi  now  pursue  a  straight 
course  towards  the  periphery  of  the  lung,  at  the  same  time  giving  off  branches  spirally.  The 
last  divide  dichotomously  and  result  in  the  terminal,  ultimate,  or  capillary  bronchi. 

phery  of  the  organ  alone  would  contain  minute  bronchi.     The  arrange- 
ment is,  however,  such  as  to  give  every wh ere  throughout  the  lung, 


BRONCHIAL   TUBES.  95 

bronchial  twigs,  terminal  or  capillary  bronchi,  from  one-one  hundredth 
to  one-two  hundredth  of  an  inch  in  diameter,  as  follows: 

The  dichotomous  subdivision  is  continued  until  the  resulting 
branches  become  reduced  to  about  one-sixth  of  an  inch  in  diameter, 
when  this  mode  of  division  ceases,  and  the  resulting  tubes  are  projected 
radially  toward  the  periphery  of  the  lung.  As  the  straight  tubes 
pursue  their  course,  side  branches  are  given  off  in  spiral  succession. 
The  side  tubes  themselves  give  off  branches  which  divide  dichoto- 
mously  into  the  terminal  bronchi.  The  straight  tubes  constantly 
dimmish  in  size,  and  ultimately  divide  and  result  also  in  terminal 
bronchi.  The  diagram  (Fig.  69)  is  intended  to  illustrate  this  plan 
of  subdivision,  but  it  is  purely  schematic. 

A  typical  bronchial  tube  (Fig.  71)  presents  four  coats  as  follows: 

1.  Epithelial. 

2.  Internal  fibrous  or  mucosa. 

3.  Muscular  or  muscularis  mucosce. 

4.  External  fibrous  or  submucosa. 

The  lining  epithelium  is  composed  of  cylindrical  cells,  provided  on 
their  free  extremities  with  delicate  hair-like  appendages — the  cilia. 
Between  the  pointed,  attached  end  of  the  ciliated  cells,  small  ovoid 
cells  are  wedged,  and  the  whole  rests  upon  a  layer  of  round  cells. 
The  epithelium  pursues  a  wavy  course,  so  that  the  lumen  of  a  tube 
appears  stellate  rather  than  circular  in  transverse  section.  This 
greatly  increases  the  extent  of  surface. 

The  internal  fibrous  coat  or  mucosa  is  composed  of  a  small  amount 
of  connective  tissue,  which,  just  beneath  or  outside  the  epithelium, 
sustains  collections  of  adenoid  or  lymphoid  tissue.  In  the  pig,  a  con- 
siderable quantity  of  yelloiv  elastic  tissue  is  found  in  the  mucosa  out- 
side the  adenoid  tissue,  but  the  amount  is  smaller  in  man.  The  fibres 
are  for  the  most  part  disposed  longitudinally.  Many  nutrient  vessels 
from  the  bronchial  artery,  capillaries,  venules,  and  lymph-spaces  are 
also  found  in  this  coat. 

The  muscular  coat — muscularis  mucosse — does  not  differ  from  the 
same  layer  in  other  mucous  membranes.  Its  thickness  varies  in  pro- 
portion to  the  size  of  the  bronchus,  the  smaller  tube  possessing  rel- 
atively the  thicker  walls.  The  fibres  pass  circularly,  and  are  of 
the  non-striated  or  involuntary  variety. 

The  external  coat  or  submucosa  is  largely  composed  of  loose  con- 
nective tissue,  the  fibres  being  mostly  arranged  circularly.  A  few 
delicate  elastic  fibres  run  longitudinally.  The  external  fibres,  like 
those  of  all  tubes,  ducts,  and  vessels,  are  for  the  purpose  of  establish- 
ing connection  with  the  organ  or  part  traversed;  so  that  it  is  often 


VO  PRACTICAL    MICROSCOPY. 

difficult  to  demonstrate  the  exact  external  limit  of  a  bronchus.  This 
coat  is  liberally  supplied  with  nutrient  branches  from  the  bronchial 
artery. 

The  elasticity  and  strength  of  the  larger  and  medium-sized  bronchi 
are  greatly  increased  by  the  presence  of  cartilage  in  the  form  of 
plates,  which  are  imbedded  in  the  external  coat.  They  are  not  uni- 
form in  size,  neither  are  they  placed  regularly.  They  frequently 
overlap  one  another,  and  two  or  three  may  be  superposed.  As  the 
tubes  become  reduced  in  size  the  plates  become  diminished  in  fre- 
quency— disappearing  altogether  when  a  diameter  of  about  one- 
twentieth  of  an  inch  has  been  reached.  The  cartilage  is  of  the 
hyaline  variety;  and  each  plate  is  covered  with  a  dense  fibrous  coat, 
the  perichondrium,  which  unites  it  with  contiguous  parts. 


FIG.  70. -TRANSVERSE  SECTION  OF  A  PORTION  OP  HUMAN  LUNG,  SHOWING  A  SMALL  BRONCHUS. 

Stained  with  Haema. 

A.  Lumen  of  bronchus. 

B.  Ciliated  columnar  epithelium. 

C.  Internal  fibrous  layer— Mucosa. 

D.  Muscular  coat. 

E.  External  fibrous  layer— Submucosa. 

F.  Pulmonary  artery. 

G.  Nerve. 

H,  H,  H.    Pulmonary  alveoli  surrounding  bronchus.   X  60. 

The  principal  bronchi  are  provided  with  a  great  number  of  mucous 
glands,  which  are  located  in  the  external  coat  or  submucosa.  They 
are  simple,  coiled  tubular  glands;  commencing  on  the  inner  surface, 
penetrating  the  mucosa  and  muscularis  mucosae,  and  terminating  in 
the  submucosa,  generally  within  the  cartilage  where  they  are  coiled 
in  short,  close  turns  resembling,  in  sections,  somewhat  the  larger 


BRONCHUS   OF    PIG.  97 

sweat  glands  of  the  skin.  The  ciliated  epithelium  of  the  bronchus 
is  continued  down  the  beginning  of  the  tube  for  a  short  distance, 
after  which  the  cells  are  shortened,  and  lose  their  cilia.  The  coiled, 
gland-part  of  the  tube  is  lined  with  conical  cells,  which  are  so  large 
as  to  leave  the  lumen  very  small.  Sometimes,  and  especially  in  the 
aged,  an  ampulliform  dilatation  of  the  tube  may  be  seen  during  its 
passage  through  the  mucosa. 

The  description  just  given  will  apply  to  large  and  medium-sized 
bronchi.  Very  important  changes  take  place  as  we  pass  to  the  ter- 
minal tubes. 

As  the  tubes  decrease  in  size^the  first  coat  to  diminish  in  thickness 
is  the  outer,  or  submucosa.  We  have  already  alluded  to  the  disap- 
pearance of  the  cartilage,  and  the  mucous  glands  are  lost  at  about 
the  same  time.  The  outer  coat  becomes,  in  the  small  bronchi,  so 
thin  as  to  be  no  longer  distinctly  demonstrable.  The  muscular  coat 
is  the  last  to  disappear.  It  remains  a  prominent  feature  of  the  tube 
as  long  as  separate  coats  can  be  distinguished.  The  epithelial  cells 
lining  the  tubes  toward  the  termini  become  shortened,  and,  getting 
lower  and  lower,  at  last  result  in  flat,  pavement  epithelium. 

The  walls  of  terminal  bronchi  (diameter  one-one  hundredth  to  one- 
two  hundredths  of  an  inch)  are  composed  of  a  slight  amount  of  con- 
nective tissue  in  which  an  occasional  non-striated  muscle-cell  and 
yellow  elastic  fibre  can  be  distinguished.  They  are  lined  with  a 
single  layer  of  flat  cells.  No  definite  layers  are  distinguishable  in 
these  bronchi.  In  a  transverse  section  the  lumen  would  appear  cir- 
cular. 

PRACTICAL  DEMONSTRATION. 

The  histology  of  the  bronchi  can  be  studied  to  best  advantage, 
using  tissue  from  a  freshly  killed  pig  or  sheep.  Short  pieces  of  tubes, 
about  one-quarter  of  an  inch  in  diameter,  from  which  most  of  the 
lung  substance  has  been  cut  away,  should  be  hardened  quickly  in 
strong  alcohol.  Transverse  sections  can  be  made  free-handed,  or 
the  tissue  may  be  infiltrated  with  bayberry  tallow  or  celloidin,  and 
cut  with  the  microtome.  Stain  with  hsema.  and  eosin,  and  mount 
in  dammar. 

TRANSVERSE     SECTION     OF    PORTION    OF    BRONCHUS 

OF   PIG.     (Fig.  71.) 
OBSERVE: 

(L.) 

1.  The  epithelial  lining:  (a)  The  wavy  course,  (b)  Regions 
occupied  by  beaker  or  goblet  cells.  (The  letter  E  ID  t1^  drawing 


98 


PRACTICAL    MICROSCOPY. 


leads  to   such  a  group.)     (c)  The  number  of  nuclei,  indicating  the 
presence  of  more  than  a  single  layer  of  cells. 

2.  The  mucosa.     (a)  Deeply  stained  blue  nuclei  of  the  adenoid 
tissue  just  beneath  the  epithelium,     (b)  Pink  portion  of  the  region 
below  the  adenoid  tissue.     (The  longitudinal  elastic  fibres  cut  trans- 
versely.)    (c)  Blood-vessels. 

3.  The  muscular  coat,     (a)  Apparent  solution  of  continuity  in 
places  caused  by  tubes  of  mucous  glands.     (5)  The  absence  of 
large  vessels  in  this  coat. 


FIG.  71.— TRANSVERSE  SECTION  OF  PART  OF  THE  WALL  OF  A  LARGE  BRONCHUS. 
Lung  of  Pig.    Stained  with  Haema.  and  Eosin.     X  60. 

E.    Epithelial  lining.    The  line  from  the  letter  leads  to  a  part  of  the  lining  containing  large 
mucous  cells. 

I.    The  internal  fibrous  coat. 
M.    Muscular  coat. 

C.  Cartilage  plates  of  external  fibrous  coat. 

A.  Bronchial  artery— The  pulmonary  artery  is  not  included. 

V.  Bronchial  vein. 

N.  Nerve  trunk. 

G.  Mucous  glands. 

D.  Obliquely  sectioned  duct. 


THE    PULMONARY    BLOOD-VESSELS.  99 

4.  The  external  layer,     (a)  Its  extent.     (It  includes  the  remain- 
der of  the  section.)     (b)  Large   cartilage  plates,  C,  stained  blue. 

(c)  Cartilage  cells.     (Note  their  differing  forms  and  disposition  in 
rows  next  the  surfaces  of  the  plates. )     (d)  Periosteum,  stained  pink. 
(e)  Mucous  gland  coils.     (They  are  usually  between  the  cartilage 
and   the   muscular  coat,     (f)  Section  of  bronchial   arteries   and 
veins,     (g)  Collections  of  adipose  tissue  on  the  outer  surface,     (h) 
Portion  or  whole  of  pulmonary  artery  and  medullated  nerve 
trunks  outside  of  and  accompanying  the  bronchus.     (They  do  not 
appear  in  the  illustration.) 

(H.) 

5.  Epithelial    lining,     (a)    Cilia  of    columnar    cells,     (b)   The 
ovoid  cells  between  the  tapering  columnar  cells,     (c)  The  round 
cells,  "basement  membrane,"  upon  which  the  columnar  cells  rest. 

(d)  The  goblet  or  Weaker  cells. 

6.  The  mucosa.     (a)  The  reticulum  of  the  adenoid  tissue. 
(Will  appear  only  where  the  lymph  corpuscles  have  been  accidentally 
brushed  out.)     (b)  The  transversely  divided  ends  of  the  elastic 
fibres.     (They  appear  as  a  pink  mosaic.)     (c)  Capillaries.     (They 
may  frequently  be  traced  for  a  considerable  distance  in  their  tortuous 
course.) 

7.  The  cartilage  plates,     (a)  Several  cells  in  a  single  cavity. 
(b)  The  intracellular  network. 

8.  The  mucous  glands,     (a)  That  some  of  the  cells  are  stained 
precisely  like  the  (other)  mucous  cells,  the  beakers,     (b)  If  possible, 
a  gland  tube  leading  up  to  the  lumen  of  the  bronchus.     (An  am- 
pulliform  dilatation  is  shown  in  the  upper  part  of  the  drawing.) 

THE   PULMONAEY    BLOOD-VESSELS. 

The  prominent  accompaniments  of  the  bronchus,  at  the  root  of 
the  lung,  are  the  pulmonary  artery  (carrying  venous  blood)  and  the 
pulmonary  veins. 

The  pulmonary  artery  enters  the  lung  with  the  bronchus,  following 
in  its  ramifications,  to  end  in  capillary  plexuses  in  the  wall  of  the  sac- 
like  dilatations,  which  are  in  connection  with  the  ultimate  bronchi. 
The  blood  is  then  collected  in  venules,  which  unite  to  form  the  pul- 
monary veins.  The  latter  pursue  an  independent  course  in  their  exit, 
not  accompanying  the  bronchi  until  the  root  of  the  lung  (nearly)  has 
been  reached. 

The  bronchial  artery  (nutrient)  enters  with  the  bronchus,  supplying 
its  walls  and  the  connective-tissue  framework  of  the  lung. 


100  PRACTICAL    MICROSCOPY. 

A  considerable  amount  of  connective  tissue  accompanies  and  sup- 
ports the  organs  which  enter  the  lung,  and  is  eventually  in  connec- 
tion with  the  fibrous  framework  of  the  organ. 

The  lung  will,  therefore,  be  seen  to  differ  from  organs  generally,  in 
that  it  contains  tiuo  distinct:  vascular  supplies,  viz.,  1.  The  pulmo- 
nary (of  venous  blood),  entering  for  the  purpose  of  its  own  oxygena- 
tion;  2.  The  bronchial  (arterial),  which  corresponds  to  the  usual 
nutrient  blood  supply  of  organs. 

THE   PLEUKA. 

The  lung  is  completely  enveloped  with  a  membrane  composed  ex- 
ternally of  pavement  epithelium,  while  the  visceral  portion  is  made  up 
of  interlacing  fibrous  and  elastic  tissue.  The  deep  or  visceral  layer  of 
the  pleura  sends  prolongations  in  the  form  of  septa  into  the  substance 
of  the  lung,  dividing  it  into  rounded  polyhedral  compartments  or 
lobules.  The  interlobular  septa  have  usually  become  prominent  in 
the  human  adult  from  deposits  of  inhaled  carbon  in  their  lymph 
channels. 

THE   PULMONAKY   ALVEOLI. 

The  lung  is  constantly  employed  in  maintaining  the  integrity  of  the 
blood.  This  is  accomplished  by  the  exposure  of  the  latter  to  a  con- 
tinual supply  of  atmospheric  air.  The  air  is  introduced  into  little 
sacs  (termed  air  vesicles  or  alveoli),  in  the  walls  of  which  the  blood  is 
distributed  in  a  capillary  plexus.  The  air  does  not  reach  the  capil- 
laries themselves,  inasmuch  as  they  are  covered  with  a  layer  of  flat 
cells.  These  cells,  constituting  the  parenchyma  of  the  lung,  have  the 
powder,  on  the  one  hand,  of  selecting  such  material  from  the  air  as 
may  be  required,  passing  it  on  to  the  blood  in  the  capillaries;  and,  on 
the  other,  of  removing  effete  materials  from  the  blood,  transferring  it 
to  the  atmospheric  contents  of  the  air  sacs  for  exhalation. 

The  air  sacs  or  alveoli  are  not  unlike  minute  bladders.  Their  dia- 
meter about  equals  that  of  a  terminal  bronchus,  viz.,  from  one-one 
hundredth  to  one-two  hundredth  of  an  inch.  A  group  of  these  alve- 
oli are  associated  in  the  manner  shown  in  Eig.  72,  their  contiguous 
walls  fusing  and  all  opening  into  a  common  cavity,  the  infundibulum. 
The  whole  is  in  connection  with  a  terminal  bronchus  vide  (Eig.  73). 
A  primary  lobule  having  been  thus  constructed,  several  are  associ- 
ated and  united  to  a  slightly  larger  bronchial  twig,  and  there  results 
one  of  the  polyhedral  lobules,  previously  mentioned  as  visible,  espe- 
cially on  the  surface  of  the  lung.  By  a  repetiton  of  such  elements 
the  lung  is  constructed. 


THE  PULMONARY  ALVEOLI. 


101 


The  wall  of  a  pulmonary  alveolus  or  air  sac  is  composed  of  connec- 
tive tissue,  supporting  the  capillary  network,  with  a  considerable 
amount  of  elastic  tissue  and  an  occasional  muscular  fibre.  The  whole, 
as  we  have  said,  is  lined  with  a  single  layer  of  flat  pavement  epithe- 
'lium.  The  capillary  plexus,  when  filled  with  blood,  affords  the  most 
prominent  feature  of  the  wall;  but  when  the  vessels  have  been  emp- 


FIG.  72.— DIAGRAM  OF  AN  ULTIMATE  PULMONARY  LOBULE. 

A.  A  terminal  bronchus. 

B.  The  air-sacs  or  alveoli. 

tied  of  their  contents,  they  become  very  insignificant  under  the  micro- 
scope, and  the  fibro-elastic  tissue  becomes  more  apparent.  You  will 
have  observed  that,  aside  from  the  vascular  supply,  the  histology  of 
an  alveolar  wall  resembles  very  closely  that  of  a  terminal  bronchus, 
and  when  the  vessels  are  all  empty  it  is  frequently  difficult  to  differ- 
entiate them  in  the  mounted  section. 


FIG.  73.— DIAGRAM  SHOWING  AN  ULTIMATE  PULMONARY  LOBULE  IN  LONGITUDINAL  SECTION, 
SHOWING  THE  MANNER  IN  WHICH  THE  ALVEOLI  ARE  ASSOCIATED  IN  CONNECTION  WITH  A 
TERMINAL  BRONCHUS. 

A.  Terminal  bronchus,  entering 

B.  The  infundibulum. 

C.  C,  C.    Alveoli. 

Fig.  74  shows  a  single  alveolus,  the  vessels  of  which  have  been 
injected  with  a  solution  of  colored  gelatin.  The  alveolus  has  been 
divided  through  the  middle,  and  shows  as  a  cup-shaped  cavity.  The 
fibrous  marginal  walls  are  indicated  with  their  tortuous  capillaries. 


102 


PRACTICAL    MICKOSCOPY. 


The  epithelial  cells  lining  the  bottom  are  obscured  by  the  opaque 
capillaries,  and  show  only  between  the  loops.  It  is  probable  that 
these  cells  cover  the  plexus  completely  as  they  line  the  alveoli. 

We  now  encounter  an  obstacle  which  will  frequently  be  met  in  our 
study  of  organs.  It  consists  of  the  difficulty  in  recognizing  in  sec- 
tions the  plan  of  structure  which  we  have  learned  is  peculiar  to  the 
organ  under  consideration.  For  example:  A  lung  has  been  compared 
to  a  tree.  The  bronchi  are  the  representatives  of  the  branches,  and 
the  air  sacs  of  the  fruit.  Well,  we  make  a  section  from  human  lung 
— it  matters  little  as  to  the  direction — with  every  possible  care,  and 


FIG.  74.— TRANSVERSE   SECTION   OF   A   SINGLE   PULMONARY   ALVEOLUS. 
Stained  with  Hsema.  and  Eosin.    X  400. 


Capillaries  injected. 


A,  A,  A.    Walls  of  the  alveolus. 

B,  B.    Injected  capillaries. 

C,  C.    Pavement  cells  lining  the  alveolus.    These  cells  cover  the  capillaries,  but  do  not  so  ap- 
pear in  the  drawing,  as  the  latter  are  filled  with  an  opaque  injection.    The  observer  is  supposed 
to  be  above  the  sectioned  alveolus,  viewing  the  cup-shaped  cavity. 

the  image  in  the  neld  of  the  microscope  resembles  a  fragment  of  rag- 
ged lace  more  nearly  than  anything  else  !  The  arrangement  of  the 
tubes  and  alveoli  of  the  lung  has  been  determined  by  filling  the  cavi- 
ties with  melted  wax  which,  when  cold,  and  the  tissue  destroyed  by 


LUNG   OF    PIG. 


103 


acid,  gives  a  perfect  mould  of  the  organ.     A  section  gives  us  but  a 
single  plane,  and  this  fact  must  be  always  borne  in  mind. 

PRACTICAL   DEMONSTRATION. 

With  a  very  sharp  razor,  cut  half -inch  cubes  from  pig's  lung.  Se- 
lect portions  free  from  large  bronchi,  with  the  pleura  on  one  side  at 
least,  and  harden  with  strong  alcohol.  Human  lung,  as  fresh  as  pos- 
sible, may  be  treated  in  the  same  manner.  The  epithelium  of  the 
alveoli  shows  best  in  young  lung.  Pieces  of  foetal  lung  are  easily  har- 
dened, and  should  be  studied  with  reference  to  medico-legal  work. 
Lung  must  be  made  very  hard,  or  thin  sections  cannot  be  cut.  If  the 
ordinary  95$  alcohol  does  not  harden  sufficiently,  the  process  may  be 
completed  by  transferring  the  tissue  for  twenty-four  hours  to  absolute 
alcohol.  The  celloidin  infiltrating  process  is  well  adapted  to  this 
structure. 

Stain  human  lung   sections  with  borax-carmine,  and   pig's   with 
haema.  and  eosin.     Mount  in  dammar. 


FIG.  75.— SECTION  OP  LUNG  OF  PIG. 
A,  A.    Infundibula  in  T.  S. 


Stained  with  Hsema.  and  Eosin.     x  60. 


B,  B,  B.    Alveoli;  so  sectioned  as  to  show  the  outline  only. 

C,  C,  C.    Alveoli;  so  sectioned  as  to  present  cup-shaped  cavities. 

D,  D,  D.    Alveoli;  sectioned  so  as  to  divide  the  top  (or  bottom^. 

E,  E.    Terminal  bronchi  in  T.  S. 


104 


PRACTICAL    MICROSCOPY. 


SECTION   OF  LUNG   OF  PIG-.     (Vide  Fig.  75.) 
OBSERVE: 
(L.) 

1.  The  large  scalloped  openings  A  A,  transversely  divided  infun- 
dibula. 

2.  The  divided  alveoli  B  B,  so  sectioned  as  to  cut  off  both  bottom 
and  top,  and  show  no  epithelial  lining  excepting"  at  inner  edge  of 
periphery. 

3.  The  alveoli  C  0,  divided  so  as  to  show  a  cup-shaped  bottom  or 
top.     (The  minute  granules  are  the  nuclei  of  the  lining  cells.) 

4.  The  alveoli  D  D,  so  cut  as  to  leave  most  of  bottom  or  top,  show- 
ing an  opening  in  the  centre  where  the  sac  has  been  sliced  off. 


FIG.  76.— TRANSVERSE  SECTION  OF  A  SINGLE  PULMONARY  ALVEOLUS.     Stained  with  Hsema. 

X  400. 

A.  A,  A.    Walls  of  alveolus. 

B.  Lumen. 

C.  C,  C.    Capillaries  variously  sectioned  in  their  tortuous  course. 

D.  Pavement  epithelia  intact. 

E.  Detached  pavement  cell. 

F.  Detached  cluster  of  pavement  cells. 
F'.    Granular  lining  cells. 

G.  Pulmonary  artery. 


HUMAN   LUNG.  10 5 

5.  Openings,  E  E,  which  are  about  the  same  size  and  bear  a  general 
resemblance  to  those  of  Obs.  2.  (Note  that  their  internal  edges  are 
smooth  and  not  ragged.  They  are  terminal  bronchi.  No  larger 
bronchi  have  been  included  in  the  section.) 

HUMAN    LUNG.     SECTION    SHOWING   A    SINGLE 
ALVEOLUS.     (Fig.  76.) 

OBSERVE: 

(M 

1.  The  outline   of  alveolus.     (The   alveoli  in  human   lung  will 
show  much  distortion,  as  the  tissue  cannot  be  secured  in  perfect  con- 
dition.) 

(H.) 

2.  The  fibrous  wall  A  A. 

3.  The  lumen  B.     (The  bottom  or  top  has  been  cut  off  in  making 
the  section.) 

4.  The  tortuous  capillaries  CO,  in  the  fibrous  wall.        * 

5.  The  lining  epithelial  cells,     (a)  Those  remaining  attached 
to  the  edges  of  the  wall   D.     (b)  Detached  cells  E.     (c)  Groups 
partly  detached  F. 

G.  The  divided  pulmonary  artery  G.  (A  medium-sized  bronchus- 
existed  in  the  section  immediately  to  the  left  of  the  artery.) 

7.  Portions  of  the  capillary  plexuses  in  other  alveoli-  (not  shown 
in  the  figure),  and  especially  demonstrable  when  they  may  happen  to 
contain  blood-corpuscles. 


106  PRACTICAL    MICROSCOPY. 


THE   LIVEE. 

This  great  gland  is  covered  with  a  fibrous  membrane — the  capsule 
of  Glisson.  The  capsule  is  covered  with  a  single  layer  of  irregularly 
shaped,  flat  epithelial  cells. 

Prolongations  from  the  fibrous,  visceral  portion  of  Glisson's  capsule 
penetrate  the  organ  from  every  side,  and  divide  the  entire  structure 
into  compartments,  the  lobules. 

The  hepatic  lobules  are  irregularly  polygonal  in  transverse  section, 
and  somewhat  ovoid  vertically.  They  are  about  one-twelfth  inch  in 
diameter. 

Let  us  first  examine  the  general  plan  of  the  vascular  arrangement, 
and  later,  the  minute  structure  of  the  lobular  parenchyma. 

The  hepatic  blood-supply  comes  from  two  sources:  1st,  The  venous 
drainage  from  the  chylopoietic  viscera  collected  in  the  portal  vein. 
2d,  ArterialJ  supply,  provided  directly  from  the  aorta  by  the  hepatic 
artery.  The  portal  venous  blood  is  filtered  through  the  liver  instead 
of  passing  directly  to  the  ordinary  destination  of  such  blood  (the 
cava),  in  order  to  contribute  certain  factors  to  the  processes  of  diges- 
tion and  metabolism,  while  the  smaller  arterial  supply  is  distinctly 
nutritive.  The  hepatic  duct  is  the  common  excretory  conduit  of  the 
bile  after  its  formation  by  the  parenchyma  from,  mainly,  the  portal 
blood. 

The  scheme  of  the  organ  will  be  understood  by  reference  to  Fig. 
77,  which  is  purely  diagrammatic. 

The  portal  vein  enters  the  liver  at  the  transverse  fissure.  It  divides, 
subdivides,  and,  reaching  every  part  of  the  various  lobes,  the  terminal 
twigs  are  seen  in  the  connective  tissue  of  the  walls  of  the  lobules. 

Branches  from  these  portal  termini  or  interlolular  veins  penetrate 
the  lobular  areas,  and  immediately  break  up  into  capillaries,  which 
form  an  intricate  plexus  throughout  the  lobule.  The  blood  from 
these  capillaries  is  finally  collected  in  a  central  or  intralobular  vein, 
by  means  of  which  it  is  immediately  drained  from  the  lobule. 

The  central  veins,  from  a  number  (varying)  of  the  lobules,  unite 
outside  of  the  latter,  forming  the  beginning  of  the  hepatic  or  so-called 
sublobuldr  vein*;  and,  like  vessels  from  other  lobular  areas,  unite, 
forming  several  (six  or  seven)  large  hepatic  vein*  which,  passing  in  the 
connective-tissue  framework,  finally  drain  the  blood  from  the  organ 
and  pour  it  into  the  ascending  cava  as  it  lies  posteriorly  in  its  fissure. 


THE    LIVER. 


107 


The  hepatic  artery  also  penetrates  the  transverse  fissure.  It  accom- 
panies the  portal  vein  in  its  ramifications,  giving  off  nutrient  twigs 
to  the  connective-tissue  framework  and  to  the  walls  of  the  vessels. 


The  terminal  branches,  very  minute,  pour  any  remaining  blood  into 
the  venous  plexus  at  the  margin  of  the  lobules,  thus  providing  arterial 
blood  for  the  lobular  parenchyma. 


108  PRACTICAL   MICROSCOPY. 

The  hepatic  duct  is  also  seen  emerging  from  the  transverse  fissure. 
(For  sake  of  clearness,  we  will  trace  it  from  without  inward.)  It  fol- 
lows the  courses  of  the  portal  vein  with  the  hepatic  artery.  Wherever 
in  a  section  of  the  organ  the  portal  is  divided,  the  artery  and  duct 
will  also  appear.  Bound  together  with  connective  tissue,  the  trio 
reach  the  walls  of  the  lobules.  The  ducts  now  penetrate  the  lobules 
and  break  up  into  an  exceedingly  minute  plexus — the  bile  capillaries. 
This  plexus  properly  begins  in  the  lobules  and  drains  the  bile  as 
formed,  passing  it  into  the  ducts  in  the  opposite  direction  of  the  por- 
tal blood  current, 

THE    PORTAL   CANALS. 

If  it  were  possible  to  grasp  the  vessels  as  they  are  found  emerging 
at  the  transverse  fissure,  the  portal  vein,  hepatic  artery,  and  hepatic 
duct,  and  to  forcibly  tear  them,  with  their  supporting  connective  tis- 
sue, out  of  the  liver,  a  series  of  channels  or  canals  would  thereby  be 
formed.  A  portal  canal,  then,  is  the  space  in  the  liver  occupied  by 
the  portal  vein,  the  hepatic  artery,  the  hepatic  duct,  and  the  contiguous 
connective  tissue.  Frequently  more  than  one  specimen  of  each  vessel 
is  to  be  seen  in  the  canals.  There  may  be  two  or  three  veins,  and  as 
many  arteries  and  ducts,  associated  in  a  single  portal  canal.  Lym- 
phatic chinks  are  also  abundant  in  this  connective  tissue. 

From  what  has  been  said,  it  will  be  understood  that  a  vessel  found 
by  itself  in  this  organ  must  be  either  a  centred  or  an  hepatic  vein;  and 
these  are  easily  distinguished,  as  the  former  are  within,  while  the  lat- 
ter are  without  the  lobules  and  in  the  connective-tissue  framework. 
On  the  other  hand,  a  group  of  vessels  ivill  indicate  a  portal  canal? 
with  its  large  and  thin-walled  vein,  the  small  thick-walled  artery,  and, 
intermediate  in  size,  the  duct. 

THE   LOBULAR  PARENCHYMA. 

The  lobules  consist  of  two  capillary  plexuses,  one  containing  blood 
and  the  other  bile.  In  the  meshes  of  this  network,  the  hepatic  cells 
are  located. 

The  blood  capillaries,  although  extremely  tortuous,  have  a  general 
direction  of  convergence  toward  the  central  veins.  This  is  best  seen 
when  the  lobules  have  been  divided  in  a  vertical  direction. 

The  bile  capillaries  are  among  the  smallest  canals  found  in  vascular 
tissues,  having  a  diameter  of  one-twelve  thousandth  of  an  inch.  They 
pursue  a  direction  in  the  human  liver,  as  a  rule,  at  right  angles  to 
the  course  of  the  blood  capillaries,  and  are  not  demonstrable,  except 


THE  LOBULAR  PARENCHYMA. 


109 


with  considerable  amplification,  say  X  400,  and  then  only  in  the 
thinnest  portion  of  the  sections.  They  are,  properly  speaking,  merely 
minute  channels  in  the  parenchyma,  and  have,  it  is  believed,  no  wall. 

The  hepatic  cells  are  polyhedral,  about  twice  the  size  of  a  white 
blood-corpuscle,  say  one-one  thousandth  of  an  inch,  usually  with 
a  single  nucleus  and  with  granular  protoplasm,  frequently  con- 
taining minute  fat  droplets  and  granules  of  yellow  pigment.  The 
existence  of  a  definite  limiting  membrane  has  been  questioned,  as  far 
as  the  cell  of  human  liver  is  concerned,  although  such  structure  can 
be  shown  in  many  of  the  lower  animals. 

The  physiological  plan  of  the  intralobular  structure  is  expressed  in 
the  diagram,  Fig.  78.  The  blood  is  brought  into  relation  with  the 
lobular  parenchyma — the  hepatic  cells — by  the  capillary  plexus,  and 


FIG.  78.— DIAGRAM  ILLUSTRATING  THE  INTRA-LOBULAR  HISTOLOGY  OF  THE  LIVER. 
The  hepatic  cells  are  connected  in  columns  between  the  blood  capillaries.  The  cells  are  en- 
dowed with  the  power  of  selecting,  especially,  such  materials  from  the  blood  as  are  necessary 
for  the  manufacture  of  bile.  Having  accomplished  this,  the  secreted  fluid  is  given  up  to  the  bile 
capillaries,  and  by  them  poured  into  the  ducts,  and  led  out  of  the  liver  for  subsequent  use.  The 
direction  of  the  pressure  is  indicated  by  the  arrows.  This  is  the  histology  of  gland  structures 
generally. 

the  elements  necessary  to  constitute  the  bile  are  selected  and  carried 
on,  to  be  drained  away  by  the  bile  capillaries  and  ducts. 


PRACTICAL  DEMONSTRATION. 

It  is  best  to  begin  with  the  liver  from  a  pig.  The  amount  of  con- 
nective tissue  in  the  normal  human  liver  is  very  small,  and  is  mainly 
confined  to  the  support  of  the  interlobular  vessels;  the  boundaries  of 
the  lobules  are,  therefore,  poorly  defined,  and  without  the  previous 
observation  of  some  well-outlined  specimen,  I  find  the  student  fre- 


110  PRACTICAL    MICROSCOPY. 

quently  gets   bat  an   imperfect   notion  of   the  plan  of  the   human 
organ. 

Pieces  of  liver,  say  one-half  inch  square  by  a  quarter  of  an  inch 
thick,  are  hardened  by  twenty-four  hours'  immersion  in  strong  alco- 
hol. Larger  pieces  may  be  prepared  with  Miiller's  fluid.  Sections- 
should  be  cut  with  a  microtome,  care  being  taken  to  include  the  trans- 
verse division  of  some  of  the  medium-sized  portal  canals.  The  portal 
vein,  with  its  accompanying  vessels,  may  be  easily  distinguished  from 
the  solitary  and  less  frequent  branches  of  the  hepatic  veins.  The  ele- 
ments of  these  canals,  and  especially  the  larger  ones,  are  best  kept 
intact  by  infiltration  of  the  tissue  with  celloidin;  but  very  fine  sec- 
tions may,  with  care,  be  made  from  the  alcohol-hardened  tissue. 
Even  free-hand  cuts,  after  some  degree  of  skill  has  been  obtained  by 
practice,  will  answer  very  satisfactorily.  Stain  with  haema.  and 
eosin. 

SECTION  OF  LIVER  OF  PIG.     CUT  VERTICALLY  TO  AND 
INCLUDING   THE   CAPSULE   OF   GLISSON. 

(Fig.  79.) 
OBSERVE: 

(L.) 

1.  The  capsule  of  Glisson  0.     (Note  the  prolongations  sent  into 
the  organ,  which  divide  the  entire  structure  into  irregularly  polyg- 
onal, if  divided  transversely;  and  elongated,  vertically  sectioned  areas 
— the  hepatic  lobules.) 

2.  The  central  (intra)  veins  C  V.     (Note  that  the  figure  formed 
by.  the  division  of  the  vein  varies  according  to  the  direction  of  the 
cut,  a  circle,  oval,  or  elongated  slit,  as  the  lobules  have  been  sectioned 
transversely,  obliquely,  or  vertically. ) 

3.  The  hepatic  veins  H  V.     (Those  shown  in  the  section  are  un- 
doubtedly sublobular.     It  must  be  remembered  that  sub  applied  to 
these  vessels  is  misleading,  as  the  lobules  are  situated  on  every  side,  as 
well  as  above  the  sublobular  veins.) 

4.  The  portal  canals  P  C.     (Even  the  smaller  ones,  I,  are  readily 
differentiated  from  areas  containing  hepatic  veins,   inasmuch   as   a 
group  of  vessels  can  be  distinguished — the  hepatic  veins  running  solus* 

5.  The  portal  veins  V.     (Observe  that  they  usually  present  as  the 
largest  element  of  the  canals.     Note  their  thin  walls,  the  same  fus- 
ing insensibly  with  the  surrounding  connective  tissue.     They  not  in- 
frequently contain  blood-clots,  with  deeply  stained  scattering  white 
corpuscles,  appearing  with  this  amplification  as  dots  or  granules.) 

6.  Hepatic  arteries  A.     (The  larger  examples  may  be  determined 
by  their  thick  muscular  media  and  the  wavy  pink  line — the  fenestrated 
membrane.     Several  may  be  seen  in  a  single  canal.) 


LIVER    OF    PIG. 


Ill 


7.  Hepatic  ducts   D,     (These  are  lined  with  cylindrical    cells, 
hexagonal  in  transverse  section,  and  the  bold  deeply-stained  nuclei 
give  the  ducts  marked  prominence  even  with  the  low  power.     Indeed, 
the  smaller  portal  canals  are  frequently  differentiated  by  this  element 
alone— this  being  especially  true  when  the  structures  have  been  dis- 
turbed, and  perhaps  torn,  in  the  process  of  mounting.) 

8.  The  lobular  parenchyma.     (The  arrangement  of  the  hepatic 
cells,  forming  branching  columns,  is  merely  indicated — with  the  low 


FIG.  79. -LIVER  OF  THE  PIG  SECTIONED  AT  RIGHT  ANGLES  TO  GLISSON'S  CAPSULE.    Stained  with. 

Haema.  and  Eosin.     x  60. 

C.    Capsule  of  Glisson. 

C.  V.    Central  veins. 

0.  C.    Oblique  section  of  central  veins. 

1,  I,  I.    Inter-lobular  veins.    (In  small  portal  canals) 
P.  C.    A  large  portal  canal. 

A,  A.    Hepatic  arteries. 

D.  Hepatic  duct. 
V.    A  portal  vein. 

C.    Connective  tissue  from  Glisson's  capsule. 
H,  V.    Hepatic  veins— probably  sub-lobular. 

power — by  their  deeply  stained  nuclei  presenting  granular  areas  with- 
in the  lobular  boundaries.     Still,  by  careful  attention,  the  elements 


112  PRACTICAL    MICROSCOPY. 

will  be  seen  to  radiate  more  or  less  distinctly  from  focal  points — the 
central  or  intra-lobular  veins.) 

(H.) 

9.  The  portal  veins.     (Note  the  fusing  of  the  wall  with  the  sur- 
rounding tissue — it  being  extremely   difficult   to   find  the  line   of 
demarcation.) 

10.  The  lymph   spaces  in  the  connective  tissue   of   the  portal 
canals.     (Note,  in  those  which  are  better  defined,  the  nuclei  of  the 
endothelium.     Do  not  confound  these  lymphatics  with  small  veins,  as 
the  latter  present  a  tolerably  defined  wall,  while  the  lymphatic  chinks 
appear  like  rifts  in  the  connective  tissue;  it  would 'be  difficult  to 
make  this  distinction  without  the  endothelial  cells, ) 

11.  Hepatic  arteries.     (On  account  of  its  solidity,  the  liver  will 
enable  the  student  to  secure  sections  of  blood-vessels  presenting  the 
typical  structure  more  nearly  than  the  specimens  obtained  from  the 
organs  heretofore  examined.)     Note  (a)  the  elongate  nuclei  of  the 
sarcous  elements  of  the  media  ;  (ft)  the  fusing  of  the  adventitia 
with  the  connective  tissue  surrounding  the  artery;  (c)  the  sharply  de- 
fined outer  boundary  of  the  intima — the  fenestrated  membrane, 
which,  from  the  action  of  the  hardening  agent,  has  contracted  the 
elastic  fibres  and  detached  (d)  the  endothelial  cells.     (Inasmuch  as 
the  lining  cells  of  small  arteries  are  very  frequently  partly  detached 
in  alcohol-hardened  tissue,  they  may  simulate  columnar  cells.     A  like 
appearance  is  often  presented   when  an  artery  has   been  sectioned 
obliquely,  by  the  projecting  muscle-cells  of  the  media). 

12.  Hepatic   ducts.     Note:    (a)  The  lining   cylindrical   cells. 
(b)  The  nuclei  of  these  cells  (as  a  rule,  perfectly  spherical;  and,  in 
transections  arranged  in  a  circle,  affording  an  appearance  perfectly 
characteristic),     (c)  Mucous  glands  in  the  wall  of  the  larger  ducts, 
lined  with  large  nucleated  columnar  cells,  precisely  like  those  lining 
the  duct-lumen;  and,  hence,  liable  to  be  mistaken  for  small  ducts. 
(The  tube  carrying  the  mucus  secreted  in  these  pocket-like  glands 
does  not  pass  directly  into  the  lumen  of  the  duct,  but  runs  along  ob- 
liquely, much  like   glands   in   the   bronchi.     Not   infrequently  the 
glands  possess  no  proper  efferent  tube,  but  are  mere  depressions  or 
or  diverticula  in  the  thick  wall  of  the  bile  duct.) 

13.  The  lobular  parenchyma.    (Single  cells,   partly  detached, 
may  be  found  about  the  edges  of  the  section.)     Note:  (a)  The  some- 
what polygonal  figure  ;   (b)  the  nucleus ;  (c)  nucleoli ;  (d)  fibril- 
lated,  mesh-like  cell  body ;  and  (e)  an  apparent  cell  wall.     (The 
arrangement  of  the  lobular  parenchyma  will  be  noted  in  connection 
with  the  human  liver.) 


SECTION    OF   HUMAN    LIVER.  113 

HUMAN    LIVEE. 

'        PKACTICAL   DEMONSTRATION. 

The  sections  from  which  the  illustrations  have  been  drawn  were 
made  from  material  hardened  in  Miiller's  fluid.  The  tissue  was  then 
cut,  the  sections  washed  by  six  hours'  maceration  in  water,  after 
which  they  were  treated  successively  with  alcohol  Nos*.  3,  2,  and  1, 
stained  with  hasma.  and  eosin,  and  mounted  in  dammar.  This  treat- 
ment aids  greatly  in  the  demonstration  of  the  blood  capillaries,  as 
the  contained  blood-corpuscles,  in  consequence  of  some  change 
effected  by  the'  chromium  salt,  take  the  eosin  deeply.  The  nucleoli 
of  cells  are  also  rendered  markedly  prominent. 

Pieces  of  tissue,  a  quarter  of  an  inch  square  by  half  an  inch  thick, 
may  be  hardened  in  alcohol.  This  method  will  give  very  excellent 
results,  providing  the  sections  be  cut  as  soon  as  the  hardening  process 
has  become  complete.  Stain  as  above. 

For  the  demonstration  of  the  isolated  hepatic  cells,  scrape  the  cut 
surface  of  a  piece  of  hardened  liver  with  a  scalpel,  and  throw  the 
scrapings  into  a  watch-glass  of  haema.  After  a  few  moments,  drain  off  the 
stain,  and  brush  the  stained  tissue  elements  into  a  test-tube  nearly 
filled  with  water.  Change  the  water  two  or  three  times;  and  when 
clear,  add  a  few  drops  of  eosin  solution.  Allow  the  eosin  to  stain  for 
a  moment  only;  decant,  drain,  and  fill  the  tube  with  alcohol.  After 
ten  minutes,  the  spirit  may  be  drained  off,  and  the  tube  partly  filled 
with  oil  of  cloves.  A  drop  of  the  sediment  may  then  be  placed  upon 
the  slide,  the  bulk  of  the  oil  removed  with  paper,  and  the  mounting 
completed  by  adding  a  drop  of  dammar  and  the  cover  glass.  I  am  in 
the  habit  of  keeping  this  tissue  in  the  oil,  from  year  to  year,  for  use 
in  my  classes.  If  the  oil  be  pure,  and  the  washing  thorough,  the 
staining  will  remain  unaffected  for  certainly  two  or  three  years. 

SECTION    OF  HUMAN    LIVER. 

Cut  at  right  angles  to  the  surface,  and  stained  with  hsema.  and  eosin. 

(Fig.  80.) 
OBSERVE  : 
(L.) 

1.  The  imperfectly  outlined  lobules  (in  consequence  of  the  ab- 
sence of  interlobular  connective  tissue). 

2.  The  fusing  of  the  lobules.     (At  points  like  B  B,  it  is  impos- 
sible to   say   just   where  one  lobule  ceases  and  the  contiguous  one 
begins.) 

3.  The  central  (or  intralobular)  veins  A  A — (frequently  appearing 
as  mere  slits  on  account  of  the  direction  of  the  cut). 

8 


114  PRACTICAL   MICKOSCOPY. 

4.  The  portal  canals  G  G.    (These  are  readily  detected  on  account 
of  the  deeply  stained  nuclei  of  the  cells  lining  the  hepatic  ducts. ) 

(H.) 

5.  Portal  canals   (too  small   for  demonstration  of  the  several 
elements,  but  always  distinguishable  by  the  bile-duct  cells). 

6.  The  larger  portal    canals  C.     Note:    (a)   The  large  thin- 
walled  vein  D;  (J)  The  duct  E;  (c)  The  artery  F. 


FIG.  80. -SECTION  OF  HUMAN  LIVER. 
Stained  with  Haema.  and  Eosin.    x  60. 

A.  A,  A.    Central  veins  sectioned  generally  at  right  angles  to  the  lobule. 

B.  B.    Points  where  adjoining  lobules  coalesce.    Illustrating  the  difficulty  of  outlining  the 
lobules  in  normal  human  liver. 

C.  Connective  tissue  of  a  portal  canal. 

D.  Large  interlobular  vein. 

E.  Hepatic  duct  belonging  to  C. 

F.  Hepatic  artery  of  C. 

G.  G.    Smaller  portal  canals. 

H.    Small  hepatic  ducts— always  recognizable  by  the  deeply  haema. -stained  nuclei  of  their 
lining  cells. 
I,  I.    Hepatic — sublobular — veins. 

7.  The  tortuous  course  of  the  hepatic  cell-columns  as  compared 
with  the  same  in  the  section  previously  studied. 

8.  The  hepatic  veins.    (Observe  their  infrequency  compared  with 


ELEMENTS  OF  A  PORTAL  CANAL. 


115 


the  sections  of  the  portal  veins.  Note  the  small  amount  of  connective 
tissue  around  them — greater,  however,  than  that  about  the  central 
veins. ) 


ELEMENTS  OF  A  PORTAL  CANAL.     From   previous  Section. 

(Fig.  81.) 
OBSERVE  : 

(H.) 

1.  The  portal  vein  V.     (Note  the  nuclei  of  the  few  endothelia 
remaining,  and  the  corpuscular  elements  of  the  blood  in  the  lumen 


Vie.  81.— SECTIQN  OF  HUMAN  LIVER.    SHOWING  THE  ELEMENTS  OF  A  PORTAL  CANAL. 

Stained  with  Haema.  and  Eosin.   x  400. 
A.    Hepatic  artery. 
V.  Portal  vein— interlobular. 
D.    Hepatic  duct  in  T.  S. 
D,  L.    Hepatic  duct  in  L.  S. 
L.    Lymph  space. 
The  lobular  parenchyma  of  contiguous  lobules  will  be  seen  on  the  right,  and  above  the  canal. 

of  the  vein.  Observe  that  the  white  corpuscles  are  scanty,  and  deeply 
stained,  and  that  many  of  the  colored  corpuscles  are  granular,  and 
show  loss  of  pigment  from  action  of  the  alcohol.) 


116  PRACTICAL    MICROSCOPY. 

2.  The  hepatic  artery  A.     (In  the  human  liver,  the  portal  canals 
frequently  carry  a  number  of  arteries  and  ducts,  instead  of  one  of  each, 
as  shown  in  the  one  selected  for  the  illustration.     The  arteries  can 
nearly  always  be  differentiated  by  the  clear  wavy  line  of  the  fenes- 
trated  membrane.     Should  the  section   have  been  in  a  longitudinal 
direction  with  reference  to  the  vessel,  look  for  the  elongate  nuclei  of 
the  smooth  muscle-cells  of  the  media,  some  running  with  the  artery — 
the  longitudinal — and  others  at  right  angles  to  its  course — the  cir- 
cular fibres.) 

3.  The  hepatic  duct  D.     (Observe  the  thickness  of  the  wall, 
depending,  of  course,  upon  the  diameter  of  the  duct  itself — and  the 
presence  of  connective  tissue  supporting  scattering  non-striped 
muscle-cells.    Note    the  beautiful,  clear,   columnar  cell-lining. 
That  these  cells  are  polygonal  in  transverse  section  is  demon- 
strable at  D  L,  where  the  duct  has  been  cut  in  a  longitudinal  way, 
and  the  cells  are  seen  from  above. 

4.  The  connective-tissue  element  of  the  canal,  reaching  out  in 
various  directions  between  the  adjacent  lobules. 

5.  Lymph  spaces  or  chinks  L.     (Note  the  stained  nuclei  of  the 
endothelia.) 

6.  Nerve  trunks.     (In  the  larger  canals  bundles  of  medullated 
nerves  may  be  frequently  seen.     They  are  not  shown  in  the  accom- 
panying illustration. ) 


THE    LOBULAK    PARENCHYMA.       (Fig.     82.)      STAINED 
CELLS  FEOM  HUMAN  AND  PIG'S  LIVER. 

OBSERVE: 
(H.) 

1.  Isolated   hepatic    cells  A,  A.    Note  the   large,  variably 
sized  nuclei,  their  nucleoli,  and  the  granular  protoplasm  of  the 
cell -body. 

2.  Groups  of  cells  forming  portions  of  the  hepatic  cell-columns 
as  at  C. 

3.  Cells  containing  fat  globules  D.     (This  is  not  necessarily  a 
pathological  process,  although  exactly  resembling  one,  but  the  physi- 
ological storing  of  hydrocarbons. ) 

4.  Doubly  nucleated  cells,  B. 


THE   LOBULAR   PARENCHYMA    CONTINUED. 


117 


FIG.  82.— ISOLATED  HEPATIC  CELLS. 
A,  A.    Cells  from  human  liver. 


Stained  with  Hsema.  and  Eosin.     X  400. 


B.  Cells  from  same  showing,  below,  a  blood-capillary  in  T.  S. 

C.  A  blood  capillary  with  part  of  a  column  of  cells. 

D  Human  liver  cells  in  a  condition  of  fatty  infiltration. 

E.  Isolated  cells  from  liver  of  pig,  showing  intracellular  network. 


THE   LOBULAR    PARENCHYMA    CONTINUED. 
OF   HUMAN   LIVER. 


SECTION 


Fig.  83. 
section,) 

OBSERVE: 


(Having  found  with  (L.)  a  typical  lobule  in  transverse 


(H.) 

1.  The  central  vein  C.  V.     (Note  the  exceedingly  delicate  wall 
and  search  for  a  trunk  of  the  intralobular  plexus  in  its  connection 
with  this  vein. ) 

2.  The  blood  capillaries  in  longitudinal  section,  B,  C.     (Ob- 
serve their  exaggerated  tortuosity,  bifurcation,  and  anastomoses.) 

3.  Blood  capillaries  in  transection,  T.  S.     (Should  the  capil- 
laries be  filled  with  blood,  this  demonstration  will  be  greatly  aided.) 

4.  Hepatic  cell  columns,  H.  C.     (Note  the  difficulty  with  which 
these  can  be  traced  for  any  great  distance,  on  account  of  their  irreg- 
ular and  twisted  course  throughout  the  lobule.     Observe  that  the 
lobules  are  composed  largely  of  tortuous  blood  capillaries,  between 
which  the  hepatic  cell-columns  are  placed.     Note  the   manner   in 
which  the  cells  are  disposed  around  the  blood  capillaries,  as  at 
T.  S.). 


118 


PRACTICAL    MICROSCOPY. 


5.  Bile  capillaries,  D.  (These  are  rather  difficult  of  demonstra- 
tion in  the  human  liver.  The  section  should  be  extremely  thin,  and 
a  higher  power  than  we  ordinarily  use  will  be  required.  They  are 


FIG.  83.— A  SINGLE  LOBULE  FROM  HUMAN  LIVER. 
Transverse  section.    Stained  with  Hasina,  and  Eosin.    X  400. 

C.  V.    Central  vein  of  the  lobule. 
B.  C.    Blood  capillaries  in  L.  S. 

T.  S.    The  same  in  transverse  section. 
H.  C.    Columns  of  hepatic  cells. 

D.  Bile  capillaries. 

best  made  out  at  the  junction  of  three  or  four  cells,  where  the  bile 
capillary  has  been  divided  transversely.) 

THE    LOBULAE    PARENCHYMA,    CONCLUDED.     ORIGIN 
OF   THE   BILE   DUCTS.     SAME   SECTION  AS   BEFORE. 

(Fig.  84.) 
OBSERVE: 

(H.) 

1.  The  connection  between  the  intralobular  bile  capillaries 
and  the  marginal  or  intralobular  bile  ducts.  (The  manner  of  con- 
nection between  the  above  is  as  follows:  The  bile  capillaries  are 
merely  channels  between  the  hepatic  cells,  and  run,  as  a  rule,  at 
right  angles  to  the  blood  capillaries.  They  are,  I  believe,  in  the  hu- 


THE    LOBTJLAR    PARENCHYMA    CONTINUED. 

man  liver,  destitute  of  a  wall.  As  these  channels  approach  the  mar- 
ginal part  of  the  lobule,  the  hepatic  cells  surrounding  the  capillary 
are  seen  to  change  their  form.  They  elongate,  getting  thinner,  grad- 
ually losing  their  form  as  hepatic  cells,  and  assume  a  columnar  type. 
At  the  same  time,  a  few  fibres  of  connective  tissue  are  thrown  outside 
the  modified  hepatic  cells,  and  a  bile  duct  results.  The  hepatic  cells 
become,  insensibly,  the  columnar  cells  lining  the  duct.  This  is 


FIG.  &4.— PORTION  OP  THE  PERIPHERY  OF  AN  HEPATIC  LOBULE  SHOWING  THE  ORIGIN  OF  A  BILE: 

DUCT. 
Stained  with  Heema.  and  Eosin.   x  400. 

A.  Bile  capillaries  in  longitudinal  section. 

B.  Bile  duct.    The  bile  capillaries  are  simply  chinks  between  the  hepatic  cells.    In  order  to 
tte  formation  of  a  duct,  the  hepatic  cells  are  altered  in  shape,  elongated,  and  eventually  become 
the  lining  cells  of  the  duct.    A  little  connective  tissue,  thrown  around  the  outside,  completes  the 
structure  as  seen  at  B. 

C.  Bile  capillary  in  transverse  section.    The  larger  clear  spaces  are  blood  capillaries. 

shown  in  the  illustration  rather  diagrammatically.  Its  demonstration 
requires  much  patient  study  and  search.  The  duct  is  best  traced 
backward,  as  these  are  readily  found.) 


120  PRACTICAL    MICROSCOPY. 


THE  KIDNEY. 

The  kidney  is  as  singular  in  structure  as  in  function.  Although 
developed  in  lobular  form,  little  trace  of  this  remains  in  the  adult 
organ. 

The  kidney  consists,  essentially,  of  an  intricate  system  of  blood- 
vessel plexuses,  in  intimate  relation  with  a  system  of  urine  tubes — 
the  whole  supported  by  a  small  amount  of  connective  tissue. 

The  accompanying  drawing  (Fig.  85)  will  serve  to  give  an  idea  of 
the  gross  plan  or  scheme  of  the  structure — remembering  that  the 
illustration  is  only  a  diagram, 

On  making  a  vertico-lateral  section,  on  the  median  line,  the  fol- 
lowing appears: 

The  kidney  is  invested  with  a  fibrous  capsule,  which  is  connected 
with  the  parenchyma  by  very  delicate  prolongations  of  its  connective 
tissue  fibrillae.  This  capsular  investment  is  in  connection,  above, 
with  the  supra- renal  bodies;  and,  on  the  inner  border,  with  the  ves- 
sels, etc.,  which  enter  and  leave  the  organ  at  its  hilum.  The  ureter, 
penetrating  the  areolar  tissue  which  (containing  much  fat)  presents 
at  the  hilum,  may,  for  clearness  of  description,  be  traced  backward 
into  the  kidney.  This  tube  expands  into  the  pelvis,  and  reduplica- 
tions of  its  wall  imperfectly  divide  the  pelvic  area  into  three  com- 
partments, or  infundibula. 

Each  infundibulum  is  subdivided  again,  imperfectly,  into  several 
pockets  or  calyces;  and  into  each  calyx  may  be  seen,  peeping  from 
the  kidney  substance,  a,  papillary  eminence  or  apex  of  a  cone — the 
pyramids  of  Malpighii.  The  pelvis  is  lined  with  a  variety  of  transi- 
tional or  imperfectly  stratified  epithelium,  which  will  be  described 
hereafter. 

The  blood-vessels,  lymphatics,  etc.,  pass  in  at  the  hilum,  outside 
the  ureter,  pelvis,  and  infundibula.  The  artery  divides  into  numer- 
ous branches  which  are  seen  in  the  diagram  passing  outward,  between 
the  Malpighian  pyramids.  The  renal  vein  pursues  much  the  same 
course,  the  main  trunks  lying  side  by  side. 

On  examining  a  section  of  the  kidney,  made  in  the  direction  indi- 
cated in  Fig.  85,  a  division  will  be  manifest  of  an  outer  portion, 
bounded  by  the  capsule  externally,  of  granular  texture,  containing 
the  blood-vessels,  etc.  This  is  called  the  cortex.  Within  the  corti- 
cal portion  there  appear  a  number  of  pyramidal  masses — whose  apices 


THE     KIDNEY. 


121 


we  have  previously  seen — of  finely  striated  texture — the  medullary  or 
Malpighian  pyramids.  The  cortical  substance  projects  itself  between 
the  pyramids,  completely  isolating  them,  forming  the  cortical  columns. 
Again  observing  the  outer  cortex,  it  will  present  narrow,  light- 
colored  lines,  which  converge  toward  the  pelvis;  and,  eventually, 
pass  into,  and  become  a  part  of  the  Malpighian  pyramids.  These 


FIG.  85.— DIAGRAM  SHOWING  THE  PI.AN  OF  STRUCTURE  OF  THE  HUMAN  KIDNEY. 

light  areas,  made  up  of  urine  tubules,  are  the  pyramids  of  Ferrein,  or, 
as  sometimes  called,  the  medullary  radii. 

The  darker  spaces  between  the  pyramids  of  Ferrein  are  called 
labyrinths. 

The  gross  elements,  to  be  understood  before  we  proceed,  then,  are: 

1.  The  capsule  of  the  kidney. 

2.  The  ureter. 

3.  The  pelvis  with  its  three  infundibula.     The  subdivision  of  each 


122  PRACTICAL     MICROSCOPY. 

infundibulum  into  several  calyces.     Each  calyx  the  site  of  the  apex  of 
a  Malpighian  pyramid. 

4.  The  blood-vessels  entering  and  leaving  the  hilum.     Their  subdi- 
vision outside  the  pelvic  lining,  and  final  passage  into  the  kidney  sub- 
stance in  the  cortical  columns. 

5.  Division  of  kidney  substance  into  cortex  and  medullary  or  Mal- 
pighian pyramids. 

6.  Penetration  of  cortical  tissue  inward  between  pyramids  of  Mal- 
pighii — constituting  the  cortical  columns. 

5.  The  pyramids  of  Ferrein. 

6.  The  labyrinths. 

In  the  domestic  animals  there  are  no  cortical  pyramids — the  pyra- 
mids of  Malpighii  coalescing,  as  it  were — thus  presenting  a  true 
medulla. 

I  have  remarked  that  the  kidney  is  made  up  largely  of  urine-carry- 
ing vessels  (the  tubuli  uriniferi)  and  blood-vessels.  We  will  first 
study  the  tubular  system,  reserving  for  the  present  the  consideration 
of  the  blood-vessel  arrangement. 

THE   TUBULI   UKIXIFERI. 

The  urine-carrying  tubules  commence  in  the  cortex,  and,  after  tak- 
ing a  very  circuitous  route  with  frequently  varying  diameter,  the 
tubes  end  at  the  apex  of  the  pyramids  of  Malpighii,  where  they  pour 
their  contained  urine  into  the  calyces.  The  urine  then  overflows  into 
the  infundibula,  and  is  finally  drained  from  the  pelvis  by  the  ureter. 

We  shall  begin  with  a  single  typical  tube;  and,  understanding  its 
histology,  we  can  build  up  the  organ,  by  simply  multiplying  this 
element. 

A  uriniferous  tube,  or  tubule,  commences  in  the  cortex  in  a  laby- 
rinth (between  the  pyramids  of  Ferrein),  as  a  thin-walled  (g-sVo")  sac 
(riV')-  This  vesicle,  with  contents,  is  a  Malpighian  body;  and  its  wall 
is  called  the  capsule  of  the  same,  or  the  capsule  of  Bowman.  It  is 
made  up  of  connective  tissue  and  is  the  thickest  part  of  the  urinifer- 
ous tube  wall  or  membrana  propria,  the  remaining  portion  being 
thin  and  homogeneous. 

From  one  side  of  this,  the  expanded  beginning  of  the  tube,  a 
narrow  neck  (ToVo- ")  is  projected,  which  immediately  widens  (TJ~o  ") 
into  a  tube — the  proximal  convoluted.  This  tube  (or  this  portion  of 
the  tube)  pursues  a  very  tortuous  course,  always  keeping  between 
Ferrein's  pyramids,  and  finally  approaches  the  base  of  a  Malpighian 
pyramid.  Here  it  assumes  an  irregular  spiral  form — the  spiral  tube 

Wo")- 


THE     KIDNEY. 


123 


The  tube  suddenly  narrows  (-g-ginr  ")>  becomes  straight,  and  passes 
into  a  pyramid  of  Malpighii.  It  reaches  sometimes  just  into  the  pyramid , 
more  frequently,  however,  passing  deeper  than  this — often  descending 
two-thirds  of  the  distance  to  the  apex;  and  is  called  the  descending 
limb  of  Henle.  Henle's  descending  limb  suddenly  turns  upon  itself, 


FIG.  86.—  DIAGRAM  SHOWING  THE  DIVISIONS  OP  A  KIDNEY  TUBULE. 

forming  a  loop;  and,  widening  (ToVg-  ")>  returns  upon  its  course  as 
the  ascending  limb  of  Henle.  It  again  enters  the  cortex,  keeping  in  a 
pyramid  of  Ferrein,  and  passes  outward  until  it  approaches  the  outer 
limit  of  the  cortex,  near  the  capsule  of  the  kidney.  Here  the  ascend- 
ing limb  of  Henle  widens  (-5-^3- ")>  forming  the  distal  convoluted, 
which  pursues  a  tortuous  course  in  the  outer  cortex.  The  distal  con- 


124  PRACTICAL    MICROSCOPY. 

voluted  then  re-enters  a  pyramid  of  Ferrein,  narrows  (-g-J-g- "),  and 
passes  a  second  time  into  a  Malpighian  pyramid,  under  the  title  of 
straight  or  collecting  tube,  or  tube  of  Bellini.  The  last,  after  reach- 
ing very  nearly  to  the  apex  of  the  pyramid,  unites  with  others  of  a 
like  character,  and  forms  principal  tubes  (TUT")-  Several  principal 
tubes  unite  to  form  a  papillary  duct  (T-J-¥  ")•  From  100  to  200  of  the 
last  open  upon  the  surface  of  the  apical  portion  of  a  Malpighian 
pyramid. 

It  must  be  borne  in  mind  that,  in  describing  the  tubular  system, 
although  such  terms  as  "convoluted  tube,"  "  looped  tube,"  etc.,  are 
employed,  these  are  not  separate  tubes,  but  only  names  applied  to 
different  portions  of  one  long  tube.  A  single  tubule,  then,  com- 
mences at  Bowman's  capsule,  becomes  narrowed  like  the  neck  of  a 
flask;  courses  as  the  proximal  convoluted  and  spiral;  descends  into, 
turns,  and  emerges  from  a  Malpighian  pyramid,  as  Henle's  looped  por- 
tion; reaches  the  extreme  cortex,  and  swells  as  the  distal  convoluted; 
and  here  ends  as  a  single  or  isolated  tubule  and  enters  a  straight  tube. 
The  straight  tubes  receive  several  distal  convoluted  termini,  at  the 
cortical  periphery,  and  pass  in  small  bundles  (forming  the  pyramids 
of  Ferrein)  directly  onward  toward  the  apex  of  a  Malpighian 
pyramid;  uniting  with  one  another  at  very  acute  angles;  the  resulting 
trunks  uniting  until  the  tube  terminates  as  a  papillary  duct. 

The  tubes  are  lined  with  epithelia;  and  these  cell  elements  con- 
stitute the  parenchyma  of  the  kidney.  The  lining  cells  are,  as  a  rule, 
of  the  columnar  variety.  Two  exceptions  are  presented,  one  of 
which  appears  in  the  flattened  cells  lining  Bowman's  capsule,  and  the 
other  in  a  like  form,  in  the  descending  limb  of  Henle's  loop.  The 
parenchyma  will  receive  attention  in  our  practical  work. 

BLOOD-VESSELS. 

The  vascular  arrangement  is  complex.  The  most  prominent  and 
essential  feature  is  afforded  in  the  existence  of  two  distinct  capillary 
plexuses. 

The  renal  artery,  as  already  described,  sends  branches  into  the 
substance  of  the  kidney.  These  pass  between  the  Malpighian 
pyramids,  and.m  the  cortical  columns.  These  arterial  trunks  arch 
over  the  bases  of  the  pyramids  of  Malpighii,  forming  the  arterial 
arcade.  From  these  arches  small  straight  branches  are  sent  outward 
toward  the  capsule  of  the  kidney,  occupying  a  position  midway  be- 
tween the  pyramids  of  Ferrein,  in  the  labyrinths.  The  last  are  the 
interlobular  arteries.  During  their  course,  they  send  off  side 
arterioles  which  penetrate  the  capsule  of  the  Malpighian  bodies. 


THE   KIDNEY. 


125 


Each  afferent  arteriole  breaks  up  into  a  capillary  plexus — the  tuft  or 
glomerulus.  The  glomerulus  does  not  entirely  fill  the  capsule,  so 
that  a  space  remains  between  the  spherical  mass  of  capillaries  and 


FIG.  87.— DIAGRAM  SHOWING  THE  ARRANGEMENT  OF  BLOOD-VESSELS  IN  THE  KIDNEY.    After 

Ludwig. 

the  flattened  cells  lining  the  body.    The  glomeruli  are  enveloped  with 
a  single  layer  of  flattened  epithelial  cells. 

The  blood  escapes  from  the  glomerulus  by  one  or  two  efferent 


126  PRACTICAL   MICROSCOPY. 

orterioles  which  emerge  from  the  capsule  close  to  the  afferent  vessel. 
The  latter  is  the  more  noticeable,  as  it  is  usually  much  the  largest. 
The  efferent  arteriole  immediately  breaks  up  into  a  second  capillary 
plexus,  which  courses  between  the  uriniferous  tubules  of  the 
labyrinths  and  of  the  pyramids  of  Ferrein.  This  second  plexus  also 
descends  between  the  elements  of  the  pyramids  of  Malpighii.  From 
the  arteries  forming  the  arcade  another  set  of  branches — the  arterialce 
rectce — is  given  off;  which,  descending  into  the  Malpighian  pyramids, 
provides  another  and  direct  arterial  supply  to  the  tubular  elements 
by  elongate  capillary  loops. 

The  course  of  the  venous  trunks  is  not  unlike  that  pursued  by  the 
arteries.  Interlobular  veins  pass  into  a  venous  arcade ;  the  former 
lying  in  the  cortical  labyrinths  parallel  with  and  close  to  the  arteries. 
In  the  medulla  the  venous  blood  is  collected  from  the  capillaries  and 
carried  to  the  bases  of  the  Malpighian  pyramids  in  small  veins— venulae 
rectae.  The  blood  from  the  cortical  intertubular  capillaries  is  col- 
lected in  the  interlobular  veins. 

A  peculiar  vascular  arrangement  exists  just  beneath  the  capsule  of 
the  kidney,  consisting  of  scattered  venous  plexuses,  the  stars  of 
Verheyen.  They  contain  blood  collected  from  contiguous  inter- 
tubular  capillaries  and  are  in  connection  with  the  summits  of  the 
interlobular  veins. 

From  what  has  been  said,  it  will  be  seen  that  the  cortical  and 
medullary  blood- supplies  are,  to  a  certain  extent,  independent  of  one 
another.  The  arteriolae  rectae  provide  a  vascular  supply  to  the 
elements  of  the  Malpighian  pyramids  even  after  many  of  the  glomer- 
uli  have  become  obliterated  by  disease. 

Nerve  and  lymphatic  elements  are  not  very  prominent  features  in 
sections  of  the  kidney.  Small  medullated  nerve  trunks  may  be  easily 
demonstrated  in  transverse  sections  of  the  cortex,  especially  near  the 
bases  of  the  medullary  pyramids,  where  they  will  be  seen,  in  company 
with  the  blood-vessels  of  the  arcades.  Lymph  channels  are  also  to  be 
seen  in  the  vicinity  of  the  vessels  of  the  hilum,  and  in  the  connective 
tissue  of  the  capsule.  The  nervous  system  of  the  kidney  would  prove 
a  valuable  field  of  labor,  and  would  well  repay  the  advanced  student's 
patient  and  earnest  investigation. 

'  The  histology  of  the  kidney  will  be  better  comprehended  by  a 
reference  to  its  functioning.  The  separation  from  the  blood  of  a 
quantity  of  water,  together  with  certain  excrementitious  matters,  is 
effected,  partly  in  the  Malpighian  bodies,  and  partly  in  the  tubules. 
The  vascular  tuft — the  glomerulus— is  covered  with  a  close  fitting 
membrane  composed  of  flat  cells.  The  blood  in  this  plexus  parts 


THE    KIDNEY.  127 

with  a  certain  amount  of  its  water,  which  passes  through  the  walls  of 
the  capillaries  and  through  the  cells  covering  them.  Whether  this  be 
due  to  osmosis  or  to  some  selective  power  of  the  cells  we  have  no 
concern — suffice  it  that  certain  salts  afterwards  appearing  in  the 
urine  do  not  leave  the  blood  at  this  point.  The  efferent  glomerular 
arteriole,  it  will  be  remembered,,  breaks  into  a  second  capillary  plexus, 
which  brings  the  blood  close  to  the  walls  of  the  convoluted  tubules. 
We  believe  that  the  cells  lining  these  tubules  select  from  the  blood, 
circulating  in  the  contiguous  capillaries,  such  effete  materials  as  es- 
caped elimination  from  the  glomeruli.  Moreover,  that  some  of  the 
water,  together  with  serum  albumin,  which  escaped  in  the  first  in- 
stance and  entered  the  proximal  convoluted  tubules,  is  here  returned 
to  the  blood  by  the  intervention  of  the  same  tubular  lining  cells 
which  excrete  the  salts.  That  in  the  cells  of  these  tubules  there 
exist  currents  in  opposite  direction — one  from  the  intertubular 
capillaries  into  the  proximal  part  of  the  tubule;  and  one  from  the 
dilute  urine  in  the  tubule  into  the  capillaries.  Without  referring 
to  any  further  work  on  the  part  of  the  kidney,  I  wish  to  impress  this 
part  of  the  structual  scheme  :  That  the  first  part  of  the  uriniferous 
tubule  is  the  prominent  excreting  part.  That  the  latter  portion  of 
the  tubule — the  portion  in  the  Malpighian  pyramids,  the  straight 
tubule — is  for  the  collection  and  drainage  of  the  urine  already  ex- 
creted. And  that  between  the  excreting  first  part  and  the  draining 
second  part,  there  exists  a  narrow  looped  tubule — the  loop  of  Henle. 
The  effect  of  this  narrowing  and  tortuosity  of  the  tubule  will  be  to 
present  a  resistance  to  the  outflow  of  urine  from  the  proximal  portion 
of  the  tubule.  The  dilute  urine,  excreted  in  the  Malpighian  bodies, 
is  held  back  for  awhile  in  the  proximal  convoluted,  and  time  given 
for  the  completion  and  perfection  of  the  excretory  processes  by  the 
tubular  parenchyma. 

PKACTICAL  DEMONSTRATION. 

The  human  kidney  is  rarely  found  in  a  perfectly  normal  condition. 
The  demonstration  can  be  made  from  the  kidney  of  the  pig,  except 
as  regards  certain  features.  The  medullary  pyramids  do  not  exist  in 
the  domestic  animals,  and  the  parenchyma  presents  very  essential 
differences  from  the  cells  of  the  human  kidney.  Still,  very  much 
can  be  learned  from  the  organ  of  the  pig,  dog,  and  rabbit.  The  tis- 
sue should  be  divided  so  as  to  permit  sections  to  be  made  parallel 
with  the  medulla,  and  to  include  both  it  and  the  cortex.  The  hard- 
ening is  best  by  Miiller's  fluid.  Small  pieces  hardened  quickly  in 
strong  alcohol,  however,  stain  very  finely  with  haema.  and  eosin. 
Very  pleasing  differentiation  may  also  be  secured  by  staining  slowly 


128  PRACTICAL    MICROSCOPY. 

in  weak  borax-carmine,  clearing  with  glycerin,  and  mounting  in  the 
same  medium. 

HUMAN    KIDNEY.       SECTION    PAEALLEL    WITH    MAL- 
PIGHIAN   PYRAMID.     STAINED    WITH    H^MA.  AND 

EOSIN. 

(Fig.  88.) 
OBSERVE: 

(Naked  eye.) 
1.  The  thickness  of  the  cortex,  and  its  granular  appearance 

as  compared  with  the  medullary  portion. 


FIG.  88.— SECTION  OF  HUMAN  KIDNEY,  CUT  PARALLEL  TO  THE  PYRAMIDS  OF  FERREIN.    SHOWING 
THE  CORTEX  AND  PART  OF  A  MALPIGHIAN  PYRAMID.    X  30. 

A,  A.    Capsule  of  kidney. 

B,  B.    Pyramids  of  Ferrein. 

C,  C.    Cortical  labyrinths. 

D,  D.    Malpighian  bodies.    Many  of  the  glomeruli  drop  out  in  the  course  of  preparation,  and 
such  empty  capsules  of  Bowman  appear  as  light  circular  spots. 

E,  E.    Interlobular  arteries. 

F,  F.    Boundary  region. 

G,  G.    Transverse  sections  of  vessels  of  the  arcades. 
H.    Base  of  a  Malpighian  pyramid. 


THE    KIDNEY. 

2.  The  "markings  of  the  cortex."     These  consist  of  alternat- 
ing light  and  dark  lines,  radiating  from  the  bases  of  the  Malpighian 
pyramids.     The  lighter  masses   consist  largely  of  collecting    tubes, 
together  with  ascending  limbs  of  Henle's  looped  tubes — otherwise 
called  medullary  radii.      Between  these    lighter    areas  the  dark 
labyrinths  appear ;  in  which,  by  careful  attention,  the  Malpighian 
bodies  may  be  made  out  as  minute  red  dots. 

3.  A  region   just   outside   the   medullary  pyramids — not   as  well 
marked  as  the  outer  cortex,  in  which  few  Malpighian  bodies  present — 
the  boundary  region. 

4.  The  finely  striated  medullary  or  Malpighian  pyramids.    (The 
section  will  usually  include  portions  of  two  of  the  last.) 

5.  That  the  bases  of  the  pyramids  do  not  appear  as  a  sharply 
defined  line,  but  fade  into  the  boundary  region  ;  while  the  union  of 
the  latter  with  the  cortex  proper  is  equally  ill-defined. 

(L.)     Fig.  88. 

1.  The  cortical  labyrinths,  in  which  search  for  : 

(a)  Portions  of  the  interlobular  arteries,  together  with  the 
smaller  twigs  of  the  arterial  arcade. 

(b)  The  Malpighian  bodies.     (The  tuft  or  glomerulus  which, 
with  this  power,  appears  as  a  granular  mass,  is  wanting  in  numerous 
places — as  indicated  by  the  empty  capsules.) 

(c)  The   remaining  area  occupied  largely  by   the   convoluted 
tubes,  proximal  and  distal. 

2,  The  pyramids  of  Ferrein.     (Observe  that,  as  they  pass  into 
the  pyramids  of  Malpighii,  they  are  well  defined,  but  that  they  are 
lost  as  they  approach  the  region  of  the  capsule  of  the  organ.) 

(H.)     Fig.  89. 

1.  A  Malpighian  body.  (Select,  after  searching  several  fields, 
a  specimen  which  shows  either  the  afferent  or  efferent  vessel  of 
the  glomerulus.  It  will  be  very  difficult  to  find  a  capsule  con- 
nected with  the  neck  of  a  proximal  convoluted  tube,  as  they 
rarely  happen  to  be  so  sectioned.  You  may  indeed  be  obliged  to  ex- 
amine a  dozen  slides  before  you  succeed. )  Note — 

(a)  The  capsule  (of  Bowman  or  of  Muller).     (Observe  its  thick- 
ness ;  as  this  becomes  important  in  connection  with  the  pathology  of 
the  kidney.) 

(b)  The  flattened  cells,  lining  the  capsule.     (Many  of  them 
will  have  become  detached  hTthe  preparation  of  the  section.) 

(c)  The  glomerulus.     (The  great  number  of  nuclei  obscures  the 
loops  of  capillaries.     Kemember  that  the  nuclei  belong  partly  to  the. 


130 


PRACTICAL   MICROSCOPY. 


vessels,  and  partly  to  the  flattened  cells  covering  the  glomerulus. 
Endeavor  to  find  transversely  divided  loops  of  the  vessels, 
showing  blood  within.) 

(d)  That  the  glomerulus  does  not,  entirely,  fill  the  capsule. 

(e)  That  the  tuft  is  frequently  divided. 

(f)  That  the  tuft  is  usually  in  contact  with  the  capsule  at 
some  one  point,  where  search  may  be  made  for 


PIG.  89.— PART  OP  THE  CORTEX  OF  HUMAN  KIDNEY.    HIGH  POWER.    SAME  SPECIMEN  AS  FIG.  88. 

X400. 

A.  Ascending  limb  of  Henle's  loop. 

B.  Collecting  tubule— longitudinal  section. 

C.  Collecting  tubule.  The  upper  part  of  the  tube  is  not  sectioned ,  but  shows  the  attached  bases 
of  the  lining  cells;  and  thus  simulates  pavement  epithelium.     A,  B,  and  C  are  in  a  pyramid  of 
Ferrein. 

D.  Capsule  of  a  Malpighian  body.    The  emerging  tubule  is  not  shown,  as  the  body  is  in  T.  S. 

E.  Flattened  lining  cells  of  D. 

F.  Glomerulus. 

G.  Efferent  arterioles. 
.     H.    Afferent  arteriole. 

I.    Convoluted  tubules. 

J.    Ascending  limb  of  Henle. 

K.    Intertubular  capillaries. 

(g)    The  afferent   and  efferent  arterioles.      (The  afferent  is 
more   frequently   demonstrable ;   and  may  be   differentiated  by  its 


THE   KIDNEY.  131 

large  size  and  the  connection,  which  can  often  be  traced,  with  the 
interlobular  artery.) 

2.  Convoluted  tubules.     (The  convoluted  tubes  found  just  be- 
neath the    capsule  of  the  kidney  generally  belong  to  the   distal 
variety ;   and  they  are   not  as  favorable   specimens  as  the   deeper 
proximal  portions,  on  account  of   the  crowding  of  the  tubular  ele- 
ments in  the  outer  cortical  regions.     Select  a  transverse  section  and 
observe  :) 

(a)  The  thin  membrana  propria,  or  wall  of  the  the  tube.     (It 
does  not  appear  to  be  made  up  of  fibrillated  connective  tissue  ;  but, 
rather,  presents  a   homogeneous   structure.     Nuclei,  however,  may 
occasionally  be  seen,  which  apparently  belong  to  this  tissue.) 

(b)  The  peculiar  lining  cells.    (They  are  unlike  any  other  paren- 
chymatous  elements  found  in  the  body.     Note  that,  while  they  are 
evidently  of  the  columnar  or  cylindrical  type,  they  differ  greatly  in 
form  and  size.     The  protoplasm  is  hazy,  granular,  and  frequently 
striated.     They  take  a  dirty  brick-red  hue  from  the  eosin.) 

(c)  The  lumen.     (Compared  with  the  diameter  of  the  tube-wall, 
the  lumen  is  very  small,  and  presents  a  stellate  figure.     The  urine, 
in  passing  through  the  tubule,  is,  consequently,  brought  in  contact 
with  a  very  considerable  portion  of  the  parenchymatous  lining.) 

3.  The  large  proportion  of  the  cortical  area  occupied  by 
the  convoluted  tubules,  and  the  exceedingly  small  amount  of 
intertubular  connective  tissue. 

4.  The  intertubular  capillaries.     (These  are  exceedingly  small, 
and  difficult  of  demonstration  unless  they  be  filled  with  blood.     The 
nuclei  of  the  endothelial  wall  are  frequently  seen.     The  cells  of  the 
convoluted  tubules  are  not  infrequently  detached  from  the  membrana 
propria,  and  the  space  so  formed  may  be  mistaken  by  the  careless 
observer  for  longitudinal  sections  of  capillaries.     These  vessels  are 
much  better  seen  in  an  injected  kidney;  although  if  an  organ  be 
selected  containing  considerable  blood,  and  the  corpuscular  elements 
have  their  color  preserved  (as  in  bichromate  hardening),  the  vessels 
will  be  easily  demonstrated. 

5.  Ascending  limb  of  Henle's  loops,  in  the  cortical  labyrinths. 
(The  general  course  of  these  tubules  is  confined  to  the  pyramids  of 
Malpighii  and  Ferrein;   but  occasionally  one  of  them  may  be   seen 
passing  in  a  tortuous   course   toward   the  outer  cortex,  running  be-  - 
tween  the  proximal  convoluted  elements.     They  are  easily  recognized 
by  their  small  size  and  relatively  large  lumen.     They  are  lined  with 
short  columnar  or  cuboid  cells,  which  stain  deeply  blue  with  the  haema.) 

6.  The  pyramids  of  Ferrein. 


132  PRACTICAL   MICROSCOPY. 

(a)  Collecting  tubes.  (These  will  be  generally  recognized  by 
their  large  size  and  the  blue  color  of  the  staining.  They  are  lined 
with  columnar  cells,  which  are  hexagonal  in  transverse  section;  and 
this  gives  an  appearance  of  pavement  epithelium,,  when  they  are  seen 
from  above  or  below.  Endeavor  to  find  a  tube  split  through  the  cen- 
tre longitudinally  and  note  the  typical  columnar  cells,  as  they  pro- 
ject inward  from  the  membrana  propria,  toward  the  now  open  lumen.) 

(V)  The  spiral  tubules.  (These  resemble  somewhat  the  convo- 
luted tubules,  especially  as  their  cells  take  much  the  same  dirty  red 


Fio.  90.— MEDULLARY  PORTION  OF  SPECIMEN  SHOWN  IN  FIG.  88.    X  400. 

A.  Collecting  tubule  in  L.  S. 

B.  Collecting  tubule  from  above,  showing  attached  bases  of  lining  cells. 

C.  Collecting  tubule  presenting  different  appearance  of  lining  cells,  according  to  mode  of 
section. 

D.  Ascending  limb  of  Henle's  loop. 

E.  Same  as  last.    The  upper  end  of  the  tubule  not  sectioned. 

F.  Descending  limb  of  Henle's  loop.    Below  may  be  seen  the  loop  and  ascending  limb. 
Gr.    Oblique  section  of  large  collecting  tubule. 

H.    Basal,  attached  extremities  of  cells  lining  a  large  collecting  tubule. 
I.    Intertubular  capillaries. 

color.     The  cells  however,  plainly  columnar,  are  large  and  hexagonal 
in  transverse  section.     The  lumen  is  small.) 


THE   KIDNEY.  133 

(c)  Ascending  limbs  of  Henle's  loop.     (These  are  small  tubes 
and  have  already  beeu  described.) 

(d)  The  intertubular  capillaries.     (Inasmuch  as,  in  the  speci- 
imen  under  consideration,  the  vessels  of  the  pyramids  are  mostly  in 
transverse  section,  they  are  not  readily  made  out.     Especially  is  this 
true  if  the  blood-corpuscles  have  their  color  discharged.) 

7.  Elements  of  the  medullary  portion.     Fig.  90. 
(a)  Collecting  tubes.     (These  tubes  constitute  a  large  proportion 
of  the  medulla  of  the  organ.     They  have  been  already  described.    As 


PIG.  91.— TRANSVERSE  SECTION  OF  PYRAMID  OF  MALPIGHII.    SAME  TISSUE  AS  SHOWN  IN  FIG.  88. 
Stainad  with  Haema.  and  Eosin .    x  400. 

A.  Group  of  intertubular  blood-vessels. 

B.  Collecting— straight— tubules. 

C.  Descending  limb  of  Henle's  loop. 

D.  Ascending  limb  of  Henle's  loop. 

E.  Principal— collecting— tubule. 

F.  Principal  tubule.    Lower  portion  near  the  papillary  duct. 

The  ring  of  cells  will  be  seen  detached  from  the  membrana  propria  in  some  instances.    This  is 
due  to  contraction  of  the  tissue  during  the  hardening. 

the  apex  of  the  Malpighian  pyramid  is  approached,  and  the  straight 
unite  to  form  the  principal  collecting  tubes,  these  again  uniting  to 


134:  PRACTICAL    MICROSCOPY. 

form  the  papillary  ducts,  the  lining  cells  will  be  seen  to  get  shorter, 
and  the  lumina  larger.) 

(b)  Spiral  tubes.     (These   can  be,  in   many  instances,  followed 
down  from  the  pyramids  of  Ferrein;  and  examples  are  frequently  seen 
very  near  the  pelvis  of  the  kidney  in  the  cortical  columns.) 

(c)  Descending  limbs  of  Henle's  loop.     (These  tubes  are  the 
most  difficult  of  all   the  tubuli  uriniferi  to   demonstrate.     The  sec- 
tion  must  be  very  thin,  and,  even  then,   they  may  be  mistaken  for 
blood  capillaries.     Their  peculiar  feature  consists  in  the  wavy  lumen, 
which  is  produced  by  the  alternate  disposition  of  the  lining  cells.) 

(d)  Loop  of  Henle.     (The  loops  will  be  recognized  by  the  curv- 
ing of  the  tube.     They  are  lined  with  short  columnar  cells  which  are 
sharply  brought  out  by  the  haema.     On  account  of  their  course,  but 
few  complete  sections  are  seen. ) 

(e)  Ascending  limbs.     (Conveniently  traced  from  the  loop.) 
(/)  Intertubular  blood-vessels.     (Do  not  mistake  tubules  con- 
taining blood,  for  capillaries.     The  human  kidney  is  rarely  absolutely 
normal;  and  blood  is  frequently  found  outside  the  proper  channels. 
The  vessels  will   be  differentiated  by  the  histology  of   their  walls. 
Quite  a  number  of  venules  will  be  seen  running  in  groups  in  the 
medulla — the  venulce  rectce.} 

8.  The  same  elements  as  in  7.  (shown  in  a  transverse  section  of 
the  middle  of  a  Malpighian  pyramid,  Fig.  91). 


GENITO-URIKARY    ORGANS.  135 


EPITHELIUM    OF    THE    GENITOURINARY 

TRACT.  URETER,  BLADDER,  UTERUS, 

VAGINA,  ETC. 

The  lining  membrane  of  the  genitourinary  apparatus  is  of  interest 
to  the  medical  man;  particularly  in  connection  with  diseases,  whose 
diagnosis  may  be  largely  determined  by  a  microscopical  examination 
of  urinary  deposits. 

In  the  preparation  of  this  subject,  I  have  confined  myself,  rather 
closely,  to  the  consideration  of  such  portions  of  the  lining  of  the  genito- 
urinary tract  as  may  be  recognized  and  differentiated,  as  they  occur  in 
urine  and  other  fluid  discharges.  The  limit  prescribed  for  these 
pages  will  permit  little  beyond  this. 

It  is  not  always  possible  to  determine  the  origin  of  detached  cells, 
for  two  reasons,  viz. :  First,  certain  widely  separated  portions  are  very 
similarly  cell  covered;  and,  secondly,  cells  which  are  the  result  of 
proliferation  accompanying  diseased  processes,  are  quite  frequently  un- 
like the  original  type.  Still,  certain  portions  of  the  genito-urinary 
apparatus  have  a  distinctly  characteristic  epithelium;  and  to  such 
will  our  present  notice  be  directed. 

PEACTICAL   DEMONSTKATION. 

From  the  body  of  a  (preferably  young)  human  female,  as  soon  as 
possible  after  death,  remove  half-inch  cubes  of  the  organs  required, 
observing  that  the  lining  is  included.  The  outer  portions  are  of 
very  little  moment  comparatively.  Secure  pieces  from  the  os,  cervix 
and  fundus  of  the  uterus,  the  base  of  the  bladder,  the  wall  of  the 
vagina  near  the  cul-de-sac,  the  ureters,  and  the  pelvis  of  the  kidney. 

We  desire  to  prepare  the  tissue  so  as  to  keep  the  original  form  of 
cell  elements — to  avoid  contraction;  and  the  Miiller  process  will 
accomplish  this  perfectly.  Allow  the  pieces  to  remain  for  two  weeks 
in  the  bichromate  solution,  with  an  occasional  change.  Complete  the 
hardening  in  Nos.  3,  2,  and  1  alcohol,  as  usual.  Infiltrate  with  eel- 
loidin  or  bayberry  tallow,  and  let  the  sections  be  vertical  to  the 
mucous  surface.  The  tissues  should  not  be  handled  with  the  fingers, 
otherwise  the  epithelial  lining  cells  will  be  detached.  Stain  with 
haema.  and  eosin;  mount  in  dammar. 


136 


PRACTICAL   MICROSCOPY. 


UTERUS  AND   VAGINA    OF   THE    HUMAN    FEMALE    AT 

PUBERTY. 

VERTICAL   DEXTRO-SINISTRAL    SECTION  OF  THE   RIGHT  LIP   OF  THE 
OS,  AND  INCLUDING  PART  OF  THE  VAGINAL  CUL-DE-SAC. 

OBSERVE: 
(L.) 

1.  The  outline   of  the   section.     (Commencing  at  D,  Fig.   92, 
which  is  placed  in  the  internal  os,  follow  downward,  out  upon  the 


FIG.  92.— VERTICAL  DEXTRO-SINISTRAL  SECTION  OF  THE  RIGHT  HAND  SIDE  OF  THE  Os  UTERI. 
SHOWING  THE  INTERNAL  Os,  THE  EXTERNAL  Os,  THE  VAGINAL  CUL-DE-SAC,  AND  THE  UPPER 
PORTION  OF  THE  VAGINAL  WALL.  X  60. 

A.  The  letter  is  placed  in  the  internal  os. 

B.  Vaginal  cul-de-sac. 

C.  Vaginal  wall. 

D.  Columnar  epithelium  of  the  internal  os.    In  the  upper  portion  the  tubular  glands  are  well 


E.  Stratified  epithelium  of  the  vaginal  lining. 

F.  Change  at  the  external  os  from  stratified  flattened,  to  columnar  epithelium. 

external  os,  curve  upward  reaching,  at  B,  the  vaginal  cul-de-sac. 
Descend  along  the  right  vaginal  wall.) 

2.  The  irregular  surface  of  the  internal  uterine  wall.     (Caused 


UTERUS    AND    VAGINA. 

by  longitudinal  section  of  the  glandulae  uterinae  or  g.  utriculares, 
branched  tubular  glands.  These  are  increased  in  depth  during  preg- 
nancy, and  are  most  prominent  in  the  lower  portion  of  the  organ.) 

3.  The  epithelium,    (a)  The  deeply  stained  layer  lining  the 
vagina,  cul-de-sac,  and  external  os.     (b)  The  wavy  course  of 
a  as  it  covers  the  irregularly  formed  and  often  imperfect  papillae  of 
the  mucosa.     (c)  The  lighter  appearance  of  the  lining  of  the  inter- 
nal os.     (d)  Projection  of  the  last  into  the  glands,     (e)  The 
sharp  line  of  separation  between  the  deeply  stained  lining  com- 
mon to  the  vagina  and  the  lighter  lining  of  the  uterus  at  the  ex- 
ternal os  (Fig.  92,  F). 

4.  The  mucosa  of  the  uterus.     (There  are  no  sharply  defined 
regions  in  the  genito-urinary  tract  corresponding  to  the  mucosa  and 
submncosa  of  typical  mucous  membranes.     The  arrangement  gener- 
ally is  :  1,  an  epithelial  lining;  2,  a  subepithelial  structure,  consisting 
of  a  more  or  less  prominent  or  abundant  plexus  of  capillaries  sup- 
ported by  delicate  connective  tissue,    and  which  corresponds  to  the 
mucosa  of  typical  structures;  3,  loose  connective  tissue,  with  more 
or  less  muscular  tissue,  containing  larger  vessels,  not  separated  from 
the  mucosa  by  any  well-defined  line  or  muscularis   mucosa3,  which 
represents  the  submucosa;  5,  the  muscular  walls  proper,  consisting  of 
layers  in  different  directions,  frequently  irregularly  disposed  and  sel- 
dom in  distinct  fasciculas.) 

5.  The  mucosa  of  the  vagina   (less  distinct  than  that  of  the 
uterus). 

6.  The  uterine  and  vaginal  walls  (consisting  largely  of  involun- 
tary muscular  fibrils,  recognized  by  the  elongate  and  deeply  stained 
nuclei,  and  containing  numerous  thick-walled  arteries  and  irregular 
lymph  spaces). 

(H.) 

7.  The  uterine  epithelium  (Fig.  93).     (a)  That  it  consists  of  a 
single  layer  of  cells,    (b)  That  the  cells  are  columnar,  not  cylin- 
drical,    (c)  The  cells  in  transverse  section  are  polygonal,     (d)  They 
are  ciliated.     (This  demonstration  is  not  always  made;  but  if  the 
section  has  been  properly  prepared  from  uninjured  tissue,   the  cilia 
will  be  seen  without  difficulty,  and  especially  in  the  depressions  where 
they  are   somewhat  protected.)     (e)  The   cell   body  and   nucleus. 
(Note  the  elongate,  clear,  free  portion  and  the  frequent  curving  of 
the   whole.     Near    the   attached     extremities,   which    often    appear 
pointed,  note  the  small  deeply  stained  nuclei.)     (/)  The  large  mu- 
cous cells.     (These  singular  cells  appear  scattered  between  the  cyl- 
inders, with  a  clear  bulging  body,  often  six  times  the  breadth  of  the 


138  PRACTICAL  MICROSCOPY. 

ordinary  elements.)     (g)  The   absence   of  any   special  basement 
membrane. 

8.  The  abrupt  transition  from  columnar  to  flattened  cells  in 
the  epithelium  of  the  external  os.  (a)  The  shortening  of  the 
columnar  cells  as  the  point  of  change  is  approached.  (Sections 
must  be  examined  until  one  is  found  showing  this  point  well.  The 
illustration  (Fig.  93)  is  not  exaggerated,  and  a  properly  cut  and 
selected  specimen  must  exhibit  clearly  the  last  columnar  and  the 
adjoining  flattened  cell.  I  know  of  no  location  in  the  human  body 


FIG.  93.— EXTERNAL  Os  OF  FIG.  9,2.    MORE  HIGHLY  MAGNIFIED.     X  400, 

A.  Muscular  tissue  of  the  os  uteri,  with  numerous  blood-vesseis. 

B.  Capillary  plexuses  of  subepithelial  tissue — mucosa. 

C.  Ciliated  columnar  cells  covering  the  os. 

D.  Vacuolated  cells. 

E.  Shortening  of  the  columnar  cells  preparatory  to 

F.  Change  from  typical  uterine  epithelia— ciliated  columnar  cells— to  flattened,  stratified 
cells. 

G.  Papillary  structure  of  the  mucosa  of  the  external  os,  after  the  change  of  epithelium. 

where  the  change  in  form  of  cell  covering  approaches  this  in  abrupt- 
ness.) 

9.  The  vaginal  epithelium  (Figs.  93  and  94).     (a)  That  it  is  of 
the  stratified  variety,     (b)  The  deepest  line  of  cells  following  the 


UTERUS    AND   VAGINA.  139 

sinuous  line  formed  by  sectioning  the  papillary  mucosa.  (c)  That 
the  cells  are  more  or  less  flattened,  (d)  That  their  edges,  excepting 
those  of  the  surface,  are  serrated.  (The  union  is  by  a  cement  be- 
tween the  interdigitating  cell  bodies.)  (e)  The  change  in  form  as 
the  surface  is  approached.  (/)  The  surface  cells.  (These  are 
very  much  flattened,  and  so  fused  as  to  resemble,  in  longitudinal  sec- 
tion, fibres.)  (g)  Detached  surface  cells.  (At  H,  Fig.  94,  these 
are  shown  in  plan,  having  been  torn  off;  those  intact  are,  of  course, 
seen  in  profile.  Fig.  97  represents  the  same  elements  as  they  gener- 


FIG.  94.— VERTICAL  SECTION  OF  THE  VAGINAL  LINING  AT  PUBERTY.    Stained  with  Haema.  and 

Eosin.     x  400. 

A.  Sub-epithelial  capillary  plexus. 

B.  Papillary  arrangement  of  the  mucosa. 

C.  Large  blood-vessels  in  the  submucosa. 

D.  Muscular  wall  of  vagina. 

E.  Deep  cells  of  the  lining  epithelium. 

F.  Middle  strata  of  lining  stellate  cells. 
Gr.    Surface  cells  in  profile. 

H.    Surface  cells  in  plan — detached. 

ally  appear  in  a  film  of  urine.)     (h)  The  nuclei,  evenly  granular, 
usually  larger  than  a  red  blood-corpuscle,     (i)  Vacuolated  cells. 

10.  The  subepithelial  vaginal  structures,     (a)  The  large  and 
abundant  capillaries  of    the   mucosa.     (b)  The   submucosa,   not 


140 


PRACTICAL    MICROSCOPY. 


clearly  separated  from  the  superior  coat,  but  easily  recognized  by  the 
large  vessels  and  the  abundant  connective  tissue,  (c)  The  muscular 
vaginal  wall.  (Here  the  muscular  bundles  are  much  better  defined 
than  in  the  uterine  walls.) 


PELVIS   OF   THE   KIDNEY  AND   UKETEK. 

TRANSVERSE  SECTION  OF  THE  URETER  NEAR  THE  PELVIS  OF  THE 
KIDNEY,  AND  DETACHED  CELLS  FROM  THE  EPITHELIAL  LINING 

OF  PELVIS.     (Figs.  95  and  97.) 

(The  arrangement  and  form  of  the  cells  lining  the  pelvis  of  the  kid- 
ney and  the  ureters  are  precisely  similar,  and  so  far  Fig.  95  will 
represent  both.) 


FIG.  95.— TRANSVERSE   SECTION  OP   THE  URETER,  NEAR  THE  PELVIS  OF  THE  KIDNEY.    Stained 
with  Haema.  and  Eosin.     x  400. 

A.  Rich  capillary  plexus  of  the  niucosa. 

B.  Internal  circular  muscular  coat. 

C.  External  longitudinal  muscular  bundles. 

D.  Large  vessels  of  the  areolar  adventitia. 

E.  Deep  layer  of  somewhat  cubical  cells. 

F.  «'  Tailed  cells  "  of  the  middle  epithelial  lining. 

G.  Surface  cells  in  profile. 

H.    Surface  cells  in  plan— detached. 


THE  URINARY  BLADDER.  141 

OBSERVE: 
(L.) 

1.  The  relative  thickness  of  the  epithelium. 

2.  The  narrow  mucosa. 

3.  The  internal  circular  muscular  belting. 

4.  The  transversely  divided  bundles  of  the  external  longitudi- 
nal muscular  layer. 

5.  The  large  arteries  between  the  muscular  bundles. 

6.  Adipose  tissue,  more  or  less  abundant  in  the  loose  cellular  tis- 
sue surrounding  these  canals.     (This  element  will  afford  a  prominent 
feature  of  a  section  of  the  pelvis  of  the  kidney,  while  the  muscular 
tissue  will  be  seen  to  a  limited  extent  only.) 

(H.) 

7.  The  epithelium,     (a)  That  it  is  of  the  stratified  type,  though 
poorly  demonstrated,     (b)  The  broad    basal   attachment   of  the 
deep  cells,     (c)  The  elongate  form  of  the  cells  generally,     (d) 
That  the  borders  are  smooth  and  closely  adherent,  unlike  those 
of  the  vagina,     (e)  The  more  flattened  surface   cells.     (/)  The 
outline  of  the  last,  as  seen  in  the  detached  specimens,     (g)  The  very 
large  and  finely  granular  nuclei.     (These  cells  contain  peculiarly 
large  nuclei,  as  compared  with  the   size  of  the  body»     The  deeper 
examples  present  tapering  prolongations,  generally  at  one  end  only, 
and  are  hence  called  "  tailed  cells/'     They  will  not  be  confounded 
with   similarly  shaped,  though  much  larger  cells  from  the  bladder. 
The  surface  elements,  while  sometimes  nearly  circular,  generally  pre- 
sent one  or  two  incurvations  of  the  periphery,  indicating  their  con- 
nection with  the   neighboring   cells.     These   peculiarities  are  best 
exhibited  in  Fig.  97.) 

8.  (Keview  the  objects  previously  examined  with  low  power.) 


THE  URINARY  BLADDER. 

VERTICAL   SECTION   OF   IKNER   PORTION    OF  WALL.       (Fig.  96.) 

OBSERVE: 
(L.) 

1.  The  epithelial  lining,  (a)  That  it  is  formed  after  the  strati- 
fied type,  (b)  That,  as  compared  with  other  previously  studied  por- 
tions of  the  genito-urinary  tract,  the  epithelium  is  thin. 


142 


PRACTICAL    MICROSCOPY. 


2.  The  thin  mucosa  and  its  small  capillary  supply. 

3.  The  dense  muscular  portion,  not  arranged  in  bundles. 


4.  The  epithelium,     (a)  The  magnitude  of  the  cells.     (Z>)     The 
broad  based  cells  without  any  special  basement  membrane. 


FIG.  96. — VERTICAL  SECTION  OF    THE   LINING  PORTION  OP   THE  BLADDER  (MALE)   BEHIND   THE 

TRIGONE. 
Stained  with  Hsema.  and  Eosin.     X  400. 

A.  Connective  tissue  of  subepithehal  region,  containing  large  amount  of  muscular  fibre. 

B.  Scant  capillary  supply  of  subepithelial  region. 

C.  Muscular  wall  of  bladder. 

D.  Large  basement  cells  of  the  epithelial  lining. 

E.  Middle  region  of  lining. 

F.  Detached  surface  cells  showing  processes  beneath. 

G.  Thin  surface  cells  in  profile. 

H.    Squamous  surface  cells,  seen  detached,  in  plan. 
I.    Vacuolated  cells. 


(c)  The  three  regions,  viz.,  basal,  middle,  and  superficial.  (<$) 
The  form  of  the  middle  cells;  not  unlike  in  outline,  though  larger, 
those  of  the  corresponding  region  in  the  ureter.  (This  is  best  shown 
in  Fig.  97.)  (e)  The  large,  scaly,  and  often  fused  surface  epithe- 


THE    URINARY   BLADDER. 


143 


lia.  (Note  that  while  these,  when  seen  in  plan,  all  appear  flat,  it  is 
only  those  of  the  extreme  surface  that  are  simple  scales;  the  less 
superficial  examples  show,  when  viewed  in  profile,  prolongations 


FIG.  97.— CELLS  FROM  GENITOURINARY  TRACT.    ISOLATED  BY  TEASING,  AS  IN  TEXT,  x  400. 

A.  Surface  bladder  cells. 

B.  The  same  seen  partly  in  profile. 

C.  C.    Bladder  cells  from  deeperjayers. 

D.  Surface  vaginal  cells. 

E.  Vaginal  cells  from  deeper  layers. 

F.  Superficial  cells  from  pelvis  of  the  kidney  or  upper  ureter. 

G.  H.    From  the  same  as  F — deep  layers.    "  Tailed  Cells."    G  is  the  more  usual  form. 
I.    Ciliated  vaginal  cells. 

J,  K.    Cells  from  collecting  tubules  of  the  kidney. 

L.    Pus-corpuscles.    Not  stained. 

M.    Red  blood-corpuscles.    L  and  M  are  introduced  as  measurement  standards  of  comparison. 


from  the  under  surface,  by  means  of  which  union  is  effected  with 
the  deeper  cells.)  (/)  Vacuolated  cells.  (These  vacuolations  do 
not  occur  in  the  basal  layer.) 


144  PRACTICAL   MICROSCOPY. 


THE   OYART. 

The  ovary  consists  of  a  stroma  or  ground  substance  of  connective 
and  smooth  muscular  tissue,  in  which  are  scattered  various  sized 
spherical  bodies  or  Graafian  follicles. 

The  stroma  is  divided  into  three  layers  or  regions,  which  are  not 
very  sharply  differentiated. 

The  ovary  is  covered  upon  its  free  surface  with  a  single  layer  of 
cells  which  in  early  life  are  cylindrical,  becoming  shortened  with  ad- 
vancing age  until  after  the  menopause,  when  only  flattened  scales  can 
be  demonstrated. 

Immediately  beneath  the  epithelium  a  thin  layer  of  fibrous  tissue 
presents,  with  a  free  admixture  of  smooth  muscle  cells,  and  is  termed 
the  tunica  albuginea. 

The  cortex  proper,  or  second  layer,  is  distinguished  by  the  Graafian 
follicles,  which  will  be  described  later. 

The  central  portion  of  the  organ,  the  zona  vasculosa,  is  largely 
occupied  by  thick-walled  blood-vessels,  among  which  the  extremely 
tortuous  arteries  are  specially  evident.  Occasionally  may  be  seen  in 
this  region  somewhat  ovoid  nodules  in  varying  degrees  of  retrograde 
change — the  corpora  lutea.  They  present  the  phenomena  resulting 
from  the  maturation  of  the  follicle  during  menstruation.  The  accom- 
panying illustration  was  drawn  from  a  corpus  luteum  which  had  formed 
in  the  site  of  a  Graafian  follicle,  the  contents  of  which  had  escaped 
at  some  menstrual  epoch,  and  been  followed  by  impregnation. 

PEAOTIOAL  DEMONSTRATION. 

The  ovary  of  a  young  animal  is  to  be  preferred.  If  the  organ  can- 
not be  obtained  from  the  human  subject,  the  female  of  almost  any 
domestic  animal  will  provide  an  excellent  demonstration  for  the  his- 
tological  elements.  Let  the  tissue  be  hardened  with  strong  alcohol, 
and  sections  be  cut  vertically  to  the  free  surface  and  stained  with 
hsema.  and  eosin.  The  sections  should  include  at  least  one-half  the 
the  depth  of  the  organ,  so  as  to  exhibit  all  of  the  regions. 

SECTION   OF  THE   ADULT  HUMAN   OVARY.     (Fig.  98.) 
OBSERVE: 

CM 

1.  The  tunica  albuginea.  (Note  that  the  layer  is  not  of  uniform 
thickness,  and  is  composed  largely  of  smooth  muscular  tissue,  as 


THE    OVARY. 


145 


shown  by  the  numerous  elongate  nuclei.     Search  particularly  for  and 
note  the  character  of  the  epithelial  covering.) 

2.  The  cortical  layer,  containing  numerous  Graafian  follicles,  and 
possibly  a  corpus  luteum.     (Note  the  aggregation  of  the  smaller  fol- 
licles in  the  extreme  outer  portion  of  the  region.) 

3.  The  zona  vasculosa.     (Note  the  unusual  thickness  of  the  vas- 
cular walls  and  the  irregular  outline  of  section,  on  account  of  their 
tortuous  course.) 


FIG.  98.— SECTION   OP  THE   OVARY   FROM   A  WOMAN  35  YEARS  OLD.     Stained  with  Haema.  and 

Eosin.     x  250. 

A.  Surface  of  the  ovary. 

B.  Muscular  stroma. 

C.  Large  tortuous,  thick-walled  arteries  of  the  central  portion  of  the  organ. 

D.  D.    Small  Graafian  follicles  of  the  superficial  zone. 

E.  Larger  follicles  of  the  deeper  portion. 

F.  Membrana  propria  of  a  Graafian  follicle. 

G.  Membrana  granulosa  of  the  follicle.    The  line  leads  to  the  discus  proligerus. 
H.    An  ovum. 

I.    Germinal  vesicle. 

J.    Germinal  spot. 

K.    An  old  corpus  luteum. 

(H.) 

4.  The  Graafian  follicles,     (a)  Their  diameter,   varying  from 
one-one  hundredth  to  one-one  thousandth  of  an  inch,     (b)  The  mem- 
10 


146  PRACTICAL   MICROSCOPY. 

brana  propria.  (This  is  difficult  to  separate  from  the  stroma  of  the 
ovary  itself,  except  in  more  mature  follicles  than  shown  in  the  sec- 
tion.) (c)  The  membrana  granulosa.  (This,  in  general,  appears 
to  be  the  outer  layer  of  the  follicle,  on  account  of  the  difficulty  of 
separating  the  membrana  propria  from  the  stroma  proper  of  the 
ovary.  Note  that  it  is  composed,  in  the  smaller  and  less  mature  fol- 
licles, of  pavement  cells,  and  that  the  cells  become  thicker  with  matu- 
ration, until  columnar  cells  in  single  layer  result.)  (d)  The  ova. 
'(These  are  contained  within  the  follicles,  excepting  they  may  have 
become  detached  during  manipulation  of  the  section,  and  occupy  the 
:greater  area  of  the  same.)  (e)  The  zona  pellucida  (the  thin  wall  of 
the  ovum).  (/)  The  discus  proligerus.  (This  will  be  recognized 
;as  a  mass  of  polyhedral  cells,  connecting  the  ova  at  one  side  with  the 
columnar  cells  of  the  membrana  granulosa.  These  cells  will  prolif- 
erate later  in  the  development,  and  completely  inclose  the  ovum.) 
(g)  The  germinal  vesicle.  (Contained  within  the  ovum.  The  con- 
tents appear  granular;  it,  as  well  as  the  ovum,  is  fibrillated;  but  this 
demonstration  cannot  be  made  excepting  the  animal  be  killed  for  the 
purpose,  and  the  tissue  elements  fixed  before  changes,  which  quickly 
follow  death,  occur.)  (h)  The  germinal  spot.  (Appearing  as  a 
small  dot  within  the  germinal  vesicle.  The  ovum  presents  the  char- 
acteristics of  what  it  indeed  is—  a  typical  cell,  with  wall,  body,  nucleus, 
and  nucleolus. ) 

5.  The  corpus  luteum.  (The  example  shown  in  the  drawing,  as 
I  have  already  said,  was  developed  after  the  contents  of  the  Graafian 
follicle,  which  it  represents,  had  suffered  impregnation;  and  it  has 
arrived  at  the  later  stage  of  the  series  of  phenomena  connected  with 
its  development — the  stage  of  cicatrization.  The  cicatricial  tissue,  to 
which  the  letter  K  points,  indicates  the  remains  of  the  membrana 
granulosa.  Outside  is  seen  the  thickened  membrana  propria,  while 
among  the  contents  will  be  found  pigment  granules  and  fat  globules, 
imbedded  in  a  structureless,  gelatinous  stroma.  This  material  results 
from  changes  in  the  clot  of  blood  effused  after  the  escape  of  the 
ovum.  I  do  not  tabulate  these  elements,  as  it  is  extremely  improb- 
able that  the  student  will  find  a  corpus  luteum  in  precisely  the  condi- 
tion of  the  one  represented  until  he  has  examined  a  large  number  of 
specimens. ) 


DEVELOPMENT   OF   THE   OVUM.  14Y 


DEVELOPMENT  OF  THE  OVUM. 

As  has  been  previously  shown,  the  ovary  is  covered  with  epithe- 
lium; and  singular  as  it  may  appear,  the  fifty  thousand  Graafian  fol- 
licles, which  it  is  estimated  are  developed  during  the  life  of  the 
human  female,  have  their  origin  in  these  cells. 

During  foetal  life,  this  surface  epithelium  undergoes  a  very  rapid 
proliferation,  and  chains  of  cells  are  imbedded  in  the  stroma  of  the 
ovary.  A  little  later  in  the  development,  separate  portions  or  links 
of  these  chains  are  cut  off  by  the  ingrowth  of  the  stroma.  The  little 
groups  of  cells  thus  isolated  become  each  a  Graafian  follicle. 

Scattered  among  the  columnar  cells,  larger,  more  nearly  spherical 
cells  are  also  found,  the  primordial  ova.  These  are  also  imbedded  in 
the  substance,  and  one  at  least  will  always  be  found  among  the 
minute  collections  of  cells  which  have  been  isolated. 

In  the  process  of  development,  each  group  of  cells  becomes  a  Graa- 
fian follicle  with  its  contained  ovum,  the  columnar  cells  forming  the 
wall  proper,  and  the  primordial  cell  the  ovum  with  its  vesicle  and 
germinal  dot. 

PEACTICAL  DEMONSTRATION. 

The  ovary  from  a  still-born  babe  is  to  be  removed  with  the  scissors, 
exercising  the  utmost  care  that  the  surface  be  not  touched.  Place 
immediately  in  strong  alcohol,  and  in  twenty-four  hours  it  will  be  fit 
for  cutting.  Cut  extremely  thin  sections  at  right  angles  to  the  free 
surface  and  including  the  same.  Stain  with  hsema.  and  eosin. 
Mount  in  dammar. 

OYARY   OF  HUMAN  FCETUS   OF  EIGHT    MONTHS. 

(Fig.  99.) 

OBSERVE: 
(L.) 

1.  The  free  surface.     (Note  the  occasional  depressions  which 
mark  the  involution  of  epithelia.) 

2.  The  layers.     (Note  the  absence  of  demonstrable  tunica  albu- 
ginea  and  the  great  area  occupied  by  the  cortex.     The  vessels  of  the 
central  portions    are   unlike   the   ovary  of  mature   life;  large,   not 
numerous,  and  thin-walled. ) 


14:8  PRACTICAL   MICROSCOPY. 

(H.) 

3.  The  primordial  ova  of  the  surface  epithelium. 

4.  The  projecting  lines  or  chains  of  epithelium  undivided. 
(Here  the  cells  seem  rather  elongate.) 

5.  Chains  which  are  in  process  of  subdivision. 

6.  Young  Graafian  follicles  in  columns  at  right  angles  to  the 
surface  of  the  ovary. 

7.  The  discus  proligerus,  in  many  instances  yet  composed  of  flat- 
tened cells. 


FIG.  99.— SECTION  OF  OVARY  OF  CHILD.    DEATH  TEN  DAYS  AFTER  BIRTH,    x  350. 

A.  Germinal  epithelium,  covering  surface  of  the  ovary. 

B.  Primitive  ova. 

C.  C.    Projection  of  surface  epithelium  within  the  organ. 

D.  Constriction  of  the  projected  chain  or  cord  of  epithelium  and  isolation  of  portions  to  form 
Graafian  follicles. 

E.  Chain  of  Graafian  follicles.    The  stroma  is  seen  filled  with  previously  formed  follicles 
which  have  become  now  isolated. 

F.  A  large  Graafian  follicle.    It  has  been  cut  in  half;  the  ovum  has  fallen  out;  and  the  mem- 
brana  granulosa  is  seen  lining  the  cup-shaped  cavity. 

G.  Large  arteries  of  the  central  portion  of  the  ovary. 

8.  Follicles  showing  discus  proligerus  as  columnar  cells. 

9.  Follicles    showing   great  proliferation  of  discus  prolig- 
erus. 


DEVELOPMENT    OF    THE    OVUM.  149 

10.  Ova  in  early  development  from  primordial  cells,  with  gran- 
ular  vesicle. 

11.  Instances  of  development  of  two,  possibly  three,  ova  in 
a  single  follicle. 

12.  Large  blood  capillary  supply  of  cortex,   vessels  generally 
parallel  with  the  Graafian  chains. 


150  PRACTICAL    MICROSCOPY. 


THE  SUPRARENAL  CAPSULE. 

These  bodies  are  attached  by  areolar  tissue  to  the  summit  of  the 
kidneys,  and  consist  of  several  folia  or  leaflets.  An  examination  of 
one  of  these  leayes  will  give  us  an  idea  of  the  organ  as  a  whole.  The 
plan  of  structure  seems  to  be  as  follows: 

In  the  connective  tissue  which  supports  the  folia  are  found  arterial 
branches  derived  from  the  phrenic  (and  sometimes  from  the  renal 
before  it  enters  the  kidney).  These  arteries  penetrate  the  organ, 
break  up  immediately  into  capillaries,  which  finally  converge  toward 
the  centre  of  the  leaflet;  the  blood  is  here  collected  in  thin-walled 
veins,  by  which  it  is  drained  into  the  suprarenal  vein,  thus  leaving 
the  capsule. 

The  capillary  meshes  vary  in  form  and  size,  according  to  their 
position.  Near  the  circumference  of  the  leaves  the  meshes  are  small 
and  ovoid,  while,  as  the  centre  is  approached,  they  become  elongated. 
These  spaces  between  the  capillaries  are  filled  with  compressed,  glob- 
ular, nucleated  cells,  the  smaller  containing  only  perhaps  six  or 
eight,  while  the  longer  may  be  occupied  by  thirty  or  forty  of  these 
cell  elements,  which  constitute  the  parenchyma  of  the  organ.  This 
variation  in  size  of  the  cell  compartments,  contributing,  as  it  does, 
to  alter  the  appearance  of  the  different  zones  of  the  tissue,  has  given 
rise  to  a  division  into  cortex  and  medulla,  with  subdivisions  even  of 
these.  There  is  no  histological  or  physiological  difference,  as  we 
believe,  between  the  different  parts  of  the  folia  of  the  suprarenal  cap- 
sule, except  as  has  been  indicated.  The  structure  is  exceedingly 
simple,  although  its  function  is  not  settled  beyond  question. 


PKACTICAL  DEMONSTKATION. 

The  tissue  is  best  hardened  in  strong  alcohol,  and  should  be  cut 
as  soon  as  the  hardening  is  complete.  It  will  be  sufficiently  firm  to- 
ad mi  t  of  the  thinnest  sections  being  made  free-hand  or  with  a  simple 
microtome.  The  cuts,  stained  with  haoma.  and  eosin,  give  excellent 
differentiation. 


HUMAN    SUPRARENAL   CAPSULE. 


151 


HUMAN  SUPRARENAL   CAPSULE.     (Figs.  100  and  101.) 

SECTION  OF  A  SINGLE  LEAFLET,  CUT  TRANSVERSELY  TO  THE  CEN- 
TRAL VEINS.  STAINED  WITH  H^MA.  AND  EOSLN;  MOUNTED  IK 
DAMMAR. 

OBSERVE: 
(L.) 

1.  Section  of  arterial  twigs  on  the  border  of  the  leaflet. 

2.  The  convergence  of  the  parenchyma  toward  the  centre. 


FIG.  100. — VERTICAL  SECTION  OF  A  SINGLE  LEAFLET  OF  THE  SUPRA-RENAL  CAPSULE. 
Stained  with  Haema.  and  Eosin.    X  60. 

A.  Fibrous  tissues  surrounding  and  connecting  the  leaflets. 

B.  The  outer  portion,  consisting  of  small  compartments— the  so-called  cortex. 

C.  The  central,  elongated  cell-compartments — medulla. 

D.  Large  thin- walled  central  veins. 

E.  Arteries  ramifying  in  the  outer  fibrous  tissue  which  supply  the  parenchyma. 

3.  The  large  and  thin-walled  central  veins. 

4.  The  small  size  of  the  parenchymatous  areas  on  the  outer 
borders  and  their  elongation  within. 


152 


PRACTICAL    MICROSCOPY. 


(H.)    Fig.  101. 

1.  The  capillary  plexus,  forming  ovate  or  elongate  meshes. 

2.  The  compressed  globular  cells  of  the  parenchyma.     (Note 

that  the  cells  are  small  in  the  small  compartments,  as  though  crowded. 
This  is  due,  in  a  measure,  to  the  contraction  of  the  tissue  from  the 
rapid  hardening. ) 


.— SAME  SECTION  AS  FIG.  100,  MORE  HIGHLY  AMPLIFIED.    REGION  MIDWAY  BETWEEN  THE 
FIBROUS  INVESTMENT  AND  THE  CENTRE  OF  THE  LEAFLET,     x  400. 

A.  Blood  capillaries,  arising  from  the  arteries  seen  in  the  preceding  illustration;  and  ramify 
ing  in  the  connective-tissue  framework. 

B.  Compartments— lobules—  formed  by  delicate  connective-tissue  prolongations  from  the 
fibrous  capsule. 

C.  Lobular  parenchyma.    These  large  somewhat  rounded  cells  are  generally  mono-nucleated, 
contain  fat  globules,  and  are  frequently  pigmented. 

3.  The  minute  fat  globules  in  the  parenchyma.     (This  I  believe 
to  be  physiological,  and  not  unlike  the  fat  storing  observed  in  the 
parenchyma  of  the  liver.) 

4.  Yellow  pigment  granules  in  the  parenchyma. 


SALIVARY   GLANDS. 


153 


THE    SALIVARY    GLANDS.    PANCREAS. 
PLAN  OF  GLAND  STRUCTURE. 

GLANDS. 

A  gland  is  an  organ — frequently  subsidiary  to  and  located  within 
other  organs — whose  cells  manufacture  from  the  blood  products  to  be 
utilized  in  the  maintenance  of  physiological  integrity. 

Glands  are  tubes  or  cavities,  with  connective-tissue  walls  lined  with 
cells  of  a  columnar  type.  Around,  and  in  close  proximity  to  the  lin- 
ing, is  spread  a  plexus  of  blood  capillaries. 

The  essential  parts  of  a  gland  are,  therefore: 

1.  A  duct)  or  efferent  conduit  for  the  secretion. 

2.  Parenchyma,  cells  engaged  in  secretion. 

3.  A  blood-vascular  supply. 

TUBULAR  GLANDS. 

The  simplest  gland  structure  is  presented  in  the  form  of  a  tube. 
Ci-lands  are,  frequently,  little  more  than  tubular  depressions  in  mucous 


FIG.  102.— DIAGRAM.    SIMPLE  TUBULAR  GLAND. 

A.  Lining  cells— parenchyma. 

B.  Capillary  plexus,  supplying  the  parenchyma. 

C.  Connective  tissue  supporting  capillaries. 

D.  Arterial  supply. 


154 


PRACTICAL    MICROSCOPY. 


surfaces.     Examples    are  found  in    the  uterus,  stomach,  small  in- 
testine, etc. 

COILED  TUBULAR  GLANDS. 

Tubular  glands  are  often  greatly  elongated,  with  the  blind  ex- 
tremity coiled.  This  variation  presents  the  simplest  differentiation 
between  the  part  of  the  tube  which  is  secretory,  and  the  duct,  or 
drainage  part.  With  this  change  in  function  of  the  different  ex- 
tremities of  the  tube  will  occur  a  change  of  epithelium.  The  cells 
belonging  to  the  duct-end  will  usually  retain  the  columnar  form; 
while  the  actively  secreting  elements  will  become  enlarged,  more 
nearly  filling  the  tube,  and  assume  a  polyhedral  form  from  pressure. 


FIG.  103.— DIAGRAM.    COILED  TUBULAR  GLAND. 
Same  references  as  Fig.  102. 

Examples  have  already  been  seen  in  the  sweat  tubes  of  the  skin — 
sudoriferous  glands — and  the  mucous  glands  of  the  submucosa  of  the 
larger  bronchi. 

BRANCHED  TUBULAR  GLANDS. 

With  the  branching  of  the  duct  portion  of  gland  tubules,  there  usu- 
ally occurs  a  dilatation  of  the  extremities  into  alveoli,  although  pure 
examples  of  branched  tubular  glands  are  afforded  in  the  gastric  and  in- 
testinal glands,  those  of  the  cervix  uteri,  etc. 

The  most  nearly  typical  branching  of  gland-like  tubules  is  afforded 
by  the  tubuli  uriniferi  of  the  kidney — although  not  contained  in  a 


ACINOUS   GLANDS. 


155 


true  gland.     The  tubules  here  present  other    features  peculiar  to 
hem,  which  will  be  referred  to  under  the  proper  head. 


FIG.  104.— DIAGRAM.    BRANCHED  TUBULAR  GLAND. 
References  same  as  Fig.  102. 


ACINOUS  GLANDS. 

The  dilatation  of  branching  tubules,  referred  to  under  the  previous 
heading,  results  in  the  formation  of  acinous  glands.  They  are  formed 
by  the  subdivision  of  a  main  tube  or  duct,  with  repeated  branching  of 
the  secondary  tubules.  Collections  of  terminal  branches  often  result 
in  globular  masses  which  are  more  or  less  perfectly  isolated  from  one 
another  by  connective  tissue.  In  this  way  compound  acini  are  pro- 
duced, such  as  the  pancreas,  the  salivary,  mammary,  and  buccal 
glands. 

The  acini  may  be  developed  into  alveoli — as  in  the  active  mammary, 
and  in  the  sebaceous  glands.  These  are  usually  filled  with  polyhedral 
cells,  or  with  the  products  of  fatty  degeneration  of  the  same. 


156 


PRACTICAL  MICROSCOPY. 


FIG.  106.— DIAGRAM.    ILLUSTRATING  THE  PLAN  OF  ACINOUS  GLANDS. 
References  same  as  Fig.  102. 


FIG.  106.  —SECTION  OF  A  SMALL  PORTION  OF  THE  PAROTID  GLAND. 
Stained  with  Haema.  and  Eosin.     x  250. 

A.  Narrowing  of  the  duct  from  a  small  lobule,  before  entering  a  larger  duct. 

B.  Dilatation  of  a  duct  after  leaving  a  small  lobule. 

C.  Primary  lobules,  in  nearly  L.  S. 

D.  Acini  in  T.  S.  showing  the  minute  lumen. 

E.  Connective  tissue  supporting  the  gland. 

F.  Striated  muscular  fibre  adjacent  to  the  gland. 

G.  Adipose  tissue  in  the  loose  areolar  tissue. 


THE   PAROTID    GLAND. 


157 


THE  PAROTID  GLAND. 

The  Parotid,  Submaxillary ,  SuUingual,  and'  B'ueeal  Salivary 
Glands  are  typical  glandular  structures,  with  individual  peculiarities 
only  in  respect  to  the  cell  elements;  these  vary  according  to  the  nature- 
of  the  secretion  formed  in  each. 

The  parotid  is  a  compound  acinous  gland,  leading  from  which  is  a 
principal  duct — lined  with  tall  columnar  cells — which  collects  the 
fluid  saliva  from  the  different  divisions  of  the  organ. 

As  the  duct  penetrates  the  gland  it  branches  freely,  the  lumina 
becoming  smaller  and  the  cells  shorter  as  the  deeper  parts  are 
approached. 

Each  terminal  duct  is  in  connection  with  several  acini.  The  con- 
nective-tissue adventitia  of  the  duct  becomes  the  thin  wall  of  the 


FIG.  107.— SECTION  OF  PART  OF  THE  SUBMAXILLARY  GLAND.    X  250, 

A.  Narrow  duct  from  terminal  lobules. 

B.  Small  duct  in  T.  S. 

C.  Small  duct  in  oblique  section. 

D.  Transversely  divided  acini,  showing  large  lumen. 

E.  Mucus  remaining  in  the  lumina. 

F.  Striated  muscular  fibres 

G.  Adipose  tissue. 


158 


PRACTICAL    MICROSCOPY. 


acinus,  and  the  lining  cells  broaden,  frequently  become  polyhedral, 
and  are  bluntly  pointed.  The  cells  so  nearly  fill  the  acini  as  to  leave 
a  small  and  not  easily  recognized  lumen. 

The  gland  is  richly  supplied  with  blood-vessels. 


THE  SUBMAXILLARY  GLAND. 

The  submaxillary  is  presented  as  an  example  of  a  typical  mucous 
gland.  As  I  have  previously  said,  the  general  arrangement  is  not 
unlike  that  of  the  other  salivary  glands. 

Similar  structures  are  found  in  the  submucosa  of  the  mouth, 
tongue,  fauces,  trachea,  and  the  larger  bronchi. 

Its  peculiarity  appears  in  the  parenchyma,  and  will  be  noticed  later. 


FIG.  108. — SECTION  FROM  THE  PANCREAS. 

A.  Wall  of  a  large  duct. 

B.  The  somewhat  cubical  lining  cells. 

C.  Arteries. 

D.  Lumen  of  the  acini,  T.  S. 

E.  Terminal  duct  entering  a  lobule. 

F.  Acini  in  L.  S. 


THE    PANCREAS.  159 


THE  PANCREAS. 

The  histology  of  the  pancreas  is,  in  general,  that  of  a  true  serous 
^gland — e.  g.,  the  parotid.  It  has  been  called  by  physiologists  the 
abdominal  salivary  gland. 

The  cells,  constituting  the  parenchyma,  are  somewhat  smaller;  the 
lobules  less  regular  in  size  and  form;  and  the  lumen  of  the  acini 
much  less  easy  of  demonstration,  in  an  ordinary  hardened  section, 
than  the  same  in  the  parotid.  The  vascular  supply  is  also  more 
abundant. 

The  branches  of  the  pancreatic  duct  are  provided  with  a  very 
thick  adventitia,  are  lined  with  short  columnar  cells,  and  seldom 
present  the  dilatation,  which  generally  occurs  in  a  serous  gland,  on 
entering  the  lobule. 

PEACTICAL  DEMONSTRATION. 

PAKOTID   AND   SUBMAXILLARY   GLANDS,    AND   THE   PANCREAS. 

The  tissue  must  be  fresh,  divided  in  small  pieces — not  larger  than 
a  quarter  of  an  inch  cube — and  hardened  by  placing  in  ninety-five  per 
cent  alcohol  for  twelve  hours,  after  which  fresh  spirit  should  be  sub- 
stituted. If,  after  the  lapse  of  another  twelve  hours*  the  tissue  should 
not  be  sufficiently  firm,  it  should  be  placed  in  a  small  quantity  of  ab- 
solute alcohol  for  three  hours.  Sections  should  be  made  immediately 
after  hardening — as  more  prolonged  action  of  the  strong  spirit  will 
cause  the  tissue  to  contract. 

Sections  may  be  cut  with  or  without  a  simple  microtome — the 
desideratum  being  thin,  rather  than  large  cuts. 

Stain  lightly  with  haema.,  and  deeply  with  eosin. 

After  sections  of  hardened  tissue  have  been  examined,  the  glandular 
parenchyma  may  be  profitably  studied  in  teasings  from  tissue  which 
has  been  in  Miiller  twenty-four  hours.  Wash  the  teasings  on  the 
slide  with  a  liberal  supply  of  water,  removing  the  same  from  time  to 
time  with  blotting  paper.  Add  a  drop  of  haema,  solution;  and,  after 
washing  this  away,  add  a  drop  of  glycerin,  and  cover.  This 
method  is  very  generally  useful  for  teased  or  scraped  fragments  of 
glandular  structures. 

(Figs.  106,  107,  and  108.) 
OBSERVE: 
(L.) 

1.  The  connective  tissue.     (Most  abundant  in  the  parotid,  and 
least  so  in  pancreas. ) 

2.  The  ducts.     (Note  the  flattening    of  the   lining  columnar 
cells,  as  the  ducts  approach  the  acini,  until  mere  scales  result. 


160  PRACTICAL    MICROSCOPY. 

Also  the  thick  connective-tissue  adventitia,  especially  demonstrable  in1 
the  pancreas.) 

3.  The  lobules.    (These  are  formed  by  several  acini,  and  are  typical 
only  in  the  parotid — at  least  they  only  here  appear  well  formed.     It 
must  be  remembered  that  only  one  plane  is  visible,  and  that  there 
is  little  perspective.) 

4.  The  acini.    (Note  the  lumina — large  in  the  submaxillary, 
less  so  in  the   parotid,  and  least,   and  often  difficult  to  make 
out,  in  the  pancreas. 

5.  The   blood-vessels,   muscular  and  adipose  tissue.    (The 
two  latter  are  demonstrable  only  in  the  salivary  glands,  and  do  not 
belong  properly  to  the  gland  itself.     The  capsule  of  the  pancreas,  in 
common   with   such   structures   in   general,    contains  adipose.     The 
abundant  inter-acinous  capillary  plexuses  of  the  pancreas  require  the 
high  power  for  satisfactory  demonstration.) 

(H.) 

6.  The  parenchyma,      (a)   The  small  but  distinct  shortened 
columnar  cells  of  the  acini  of  the  parotid.     (Observe  that  they  are 
frequently  so  formed  that  the  convexity  of  one  cell  fits  into  the  con- 
cavity of  its  neighbor.     Where  seen  in  transverse  section,  the  outline 
is  a  polygon.     Nbte  especially  the  change  in  the  parenchymatous 
elements  as  the  terminal  duct  merges  into  an  acinus.) 

(#)  The  large,  swollen  cells  of  the  mucous  gland— submaxil- 
lary. (Observe  the  comparatively  clearness  of  the  cells.  They 
contain  a  very  delicate  reticulum,  and  their  nuclei  are  often 
obscured  and  frequently  seen  to  be  placed  at  the  junction  of  the 
cells.) 

(c)  The  rounded,  often  polyhedral  cells  of  the  pancreas.  (They 
resemble  the  parotid  elements,  although  smaller  and  less  granular.) 


THE   LYMPHATIC    SYSTEM.  161 


THE    LYMPHATIC    SYS 


The  Lymphatic  System  is  a  circulatory  apparatus  of  exceedingly 
complicated  arrangement.  It  comprises: 

1. — A  system  of  irregular  clefts  and  cavities  which  are  of  almost 
universal  distribution  in  the  more  solid  tissues,  in  the  framework 
and  parenchyma  of  organs,  around  tilood-vessels  and  viscera. 

2. — Nodules  of  sponge-like  tissue,  improperly  called  lymphatic 
glands. 

3. — Channels  of  communication,  consisting  of  capillaries  and  ducts. 

4. — A  central  reservoir — the  receptaculum  chyli. 

5. — Large  efferent  ducts,  by  means  of  which  the  contents  of  the 
system  are,  eventually,  poured  into  the  blood,  in  both  sides  of  the 
neck  at  the  junction  of  the  internal  jugular  and  subclavian  vein. 

6. — A  fluid,  lymph,  containing  numerous  nucleated  bodies  or 
lymphoid  cellst  and  various  substances  in  solution. 

The  whole  provides  a  channel  for  the  introduction  of  formed  and 
nutrient  elements  into  the  blood;  as  well  as  affording  drainage  for  the 
tissues,  the  products  of  which  are  also  emptied  into  the  blood-vascular 
system,  to  be  afterward  eliminated  by  special  organs. 

The  circulating  lymph  always  passes  in  a  direction  toward  the  ven- 
ous system.  This  current  is  established  in  some  of  the  lower  animate 
by  means  of  distinct,  pulsating,  hollow  organs,  or  lymph  hearts;  but 
no  corresponding  structure  exists  in  man,  and  the  system  becomes 
here  subordinated  to  the  blood-vascular  apparatus. 

In  man,  the  maintenance  of  the  lymph-flow  is  due  largely  to  a 
negative  pressure,  consequent  upon  the  connection  between  the  termini 
of  the  lymph-vessels  and  the  veins.  Without  doubt  the  pumping 
motion  of  the  intestinal  villi  presents  a  factor  in  the  establishment  of 
a  current  in  the  lacteals  toward  the  mesenteric  vessels.  The  perivas- 
cular  lymph  receives  an  impetus  with  each  cardiac  systole.  The 
muscular  contractions  of  inspiration  contribute  motility  to  the  con- 
tents of  the  diaphragmatic  lymph-channels,  in  a  direction  against 
gravity.  Indeed,  the  contractions  of  nearly  every  muscular  fibre, 
whether  skeletal  or  organic,  lend  their  aid  to  lymph  propulsion. 

The  direction  of  the  lymph-current  is  determined  by  valves  which 
resemble,  somewhat,  those  of  the  veins. 

Cavities  lined  with  so-called  serous  membranes,  may  be  considered 
as  expanded  lymph-channels. 
II 


162 


PRACTICAL    MICROSCOPY. 


LYMPH  CHANNELS. 

The  larger  and  more  regularly  formed  channels  for  lymph  circu- 
lation, such  as  the  mesenteric  and  thoracic  ducts,  do  not  differ, 
materially,  in  structure,  from  correspondingly  sized  veins.  The 
irregular  clefts  in  the  interstices  of  fibrous  tissues,  serving  as 
the  primitive  lymph-containing  channels,  have  been  already, 
and  repeatedly,  noticed.  Fig.  109,  although  purely  diagrammatic, 
will  serve  to  show  the  relation  of  this  system  to  the  blood-vessels.  A 
perivascular  lymphatic  channel  is  a  sort  of  tubular  investment  of  the 


MEDIA 
ADVENTITIA 
ERIVASCULAR 


FIG.  109.— DIAGRAM.    ARTERY   IN  TRANSVERSE   SECTION,   SHOWING  THE  PERIVASCULAR 

LYMPH-SPACE. 

blood-vessel,  lined  with  flattened  endothelia  sending  prolongations 
inward;  these  prolongations  branch,  and  are  finally  in  communication 
with  a  layer  of  cells  covering  the  adventitia.  In  this  manner,  in 
close  apposition  to  parts  of  the  vascular  system,  a  system  of  channels 
is  provided,  within  which  the  lymph  may  sloivly  percolate. 

The  largest  lymphatic  channels  in  the  human  body  are  the  cavities 
of  the  peritoneum  and  pleurae.  They  are  in  connection  one  with  the 
other,  and  with  the  lymphatic  system  generally;  and  these  channels 
of  communication  between  the  great  abdominal  and  thoracic  lym- 
phatic cavities  present,  perhaps,  as  the  most  convenient  and  typical 
for  demonstration. 


LYMPH  CHANNELS.  163 


PRACTICAL  DEMONSTKATION. 

LYMPHATIC  VESSELS   OF  THE   CENTRAL   TENDON"  OF   THE    DIAPHRAGM. 

(Figs.  110  and  111.) 

This  demonstration  had  best  be  made  with  tissue  from  the  rabbit, 
inasmuch  as  the  slightest  decomposition  of  the  epithelium  would  be 
fatal  to  success. 

A  small  (preferably  white)  rabbit  should  be  quickly  killed  by  de- 
capitation, and  immediately  suspended  by  the  hind  legs,  so  as  to 
thoroughly  drain  the  body  of  blood.  As  soon  as  the  blood  has  ceased 
dripping,  open  the  thoracic  cavity  by  slitting  up  the  skin  along  the 
median  line,  pushing  it  to  the  sides  and  removing  the  sternum.  In 
this  operation,  work  rapidly  and  avoid  soiling  the  internal  parts. 
Then  with  the  fingers  of  one  hand  raise  the  lungs  and  heart  from  the 
diaphragm,  and  with  a  large  camel's-hair  brush  proceed  to  quickly, 
and  quite  forcibly,  pencil  the  white  glistening  surface  of  the  central 
diaphragmatic  tendon,  moistening  the  brush  from  time  to  time  in  the 
lymph  of  the  pleural  cavity.  Should  the  quantity  of  fluid  be  small, 
add  a  little  distilled  or  previously  boiled  and  filtered  water.  The 
object  of  the  brushing  is  to  remove  the  epithelial  cells  which  cover 
the  surface,  and  which  would  otherwise  hide  the  lymph  spaces.  After 
the  pencilling,  drain  away  the  fluid,  and  pour  over  the  brushed  sur- 
face a  solution  of  one  grain  of  nitrate  of  silver  to  an  ounce  of  distilled 
water.*  Allow  the  silver  solution  to  remain  for  twenty  minutes  in 
contact  with  the  tissue,  the  body  meanwhile  being  kept  away  from 
the  bright  sunlight;  then  pour  off  the  solution,  wash  the  surface 
twice  with  distilled  water,  and  afterwards  allow  water  from  the  tap 
to  flow  over  the  parts  for  at  least  five  minutes. 

If  yon  observe  the  directions  carefully,  the  surface  of  the  tendon 
will  lose  its  original  glistening  appearance  and  become  whitish  and 
opaque. 

The  tendon,  or  such  portion  of  it  as  you  wish  to  preserve,  may  be 
cut  out  with  the  scissors  after  the  washing,  thrown  into  glycerin,  and 
placed  in  the  sunlight  until  the  surface  becomes  brown.  With  the 
forceps  tear  off  small  pieces  of  the  stained  side,  say  one-half  inch 
square,  and  examine  in  glycerin,  or  mount  them  permanently  in  the 
same  medium. 

The  demonstration  of  the  channels  of  the  lymphatic  system  is  based 
upon  the  following: 

1.  Lymph  channels  are  always,  however  small  or  irregular,  lined 
with  flattened  cells  in  a  single  layer,  i.  e.,  pavement  endothelium. 

2.  The  lining  cells  are  cemented  together  with  an  albuminous  sub- 
stance. 

*  Water  which  has  been  well  boiled  in  a  clean  vessel,  and  afterward  care- 
fully filtered,  may  be  generally  employed  in  histological  work  when  distilled 
water  is  not  available. 


164  PRACTICAL   MICROSCOPY. 

3.  Nitrate  of  silver  combines  with  the  cement,  forming  albuminate 
of  silver,  which  becomes  dark  brown  when  exposed  to  light. 

If  you  have  been  successful,  the  silver  will  have  penetrated  the  ten- 
don, and  mapped  out  the  lymph  channels,  indicating  an  outline  of 
every  lining  cell  by  means  of  a  dark  border.  Failure  will  result 
only  from  non- attention  to  cleanliness  in  the  handling  of  the  tissue; 
the  silver  in  which  case  becomes  deposited  generally  over  the  surface. 
The  margins  or  outlines  of  the  cells,  it  must  be  remembered,  are 
stained  with  the  silver.  The  nuclei  may  be  demonstrated  by  after- 
staining  with  dilute  haema.,  or  better,  borax-carmine.  The  mounting 
may  be  done  in  dammar,  although  the  elastic  fibres,  of  which  the 
matrix  of  the  tendon  is  composed,  will  become  stiff  during  immer- 
sion, and  show  a  tendency  to  curl  and  contract.  If  glycerin  be  used 
after  carmine  staining,  tissues  should  be  washed  thoroughly  in  water, 
subsequently  to  the  oxalic  acid  bath,  transferred  to  equal  parts  of 
glycerin  and  water,  and  allowed  to  remain  for  an  hour,  at  least,  before 
mounting. 

CENTRAL     TENDON      OF     THE     DIAPHRAGM.      SILVER 
STAINING.     (Vide  Figs.  110,  111.) 

OBSEBVE: 
(L.) 

1.  The  division  of  the  specimen  into  dark  and  light  areas. 
(The  dark  areas  represent  the  more  solid  portions  of  the  tissue  or  the 
partitions  between  the  channels,  and  the  light  spaces  are  the  lymph 
paths.) 

2.  The  lymph  paths — the  light  spaces.     (These  show,  with  this 
amplification,    as    irregular,    winding,    and    anastomosing   courses, 
marked  with  very  delicate  lace-like  tracery — the  silver  lines.) 

3.  Valves  of  the  lymph  paths.     (At  points,  the  paths  will  be 
crossed  by  dark  curved  lines.     These  are  imperfect  valves,  not  unlike 
a  single  cusp  of  an  aortic  valve. ) 

(H.) 

4.  Outlines  of  the  cells  lining"  the  larger  excavations  (lymph 
paths)  in  the  tissue.     (Note  that  the  cells  are  generally  elongate  in 
the  direction  of  the  lymph  path.     The  edges  are  frequently  serrated.) 

5.  Stomata,  minute  openings  at  the  junction  of  several  cells. 

6.  The  construction  of  the  valves.     (These  are  curved  against 
the  lymph  flow,  and  covered  with  cells  like  other  parts  of  the  channeL 


CENTRAL  TENDON  OF  THE  DIAPHRAGM.  165 

Note  the  change  in  form  of  the  cells  approaching  and  covering  the 
valves.) 

7.  Elastic  fibres  of  the  more  solid  parts  of  the  tendon. 

8.  Lymph  capillaries.     These  will  be  seen  in  the  partitions  be- 
tween the  larger  paths.     In  places  they  may  be  observed  emptying 
into  the  paths,  and  again  will  appear  as  simple  cavities,  according  to 
the  manner  sectioned.) 

9.  The   deeper  capillaries.     (Careful  focussing  the  portions  of 


FIG.  110.— LYMPH-CHANNELS.    CENTRAL  TENDON  OP  DIAPHRAGM  OF  RABBIT.    SILVER  STAINING. 

K60. 

The  dark  portions  represent  the  more  solid  portions  of  the  tissue. 

The  light  areas  are  the  lymph -channels;  and  the  direction  of  the  flow  is  shown  by  the 
Arrows. 

The  minute  lines  in  the  lymph-spaces  are  the  silver-stained  cement  boundaries  of  the 
pavement  cells  lining  the  channels. 

The  valves  appear  as  curved  lines  in  the  lymph-spaces. 

the  tendon  which  appear  most  solid  will  reveal  minute  cell-lined 
channels  or  capillaries.  The  student  must  remember  that  we  cannot 
penetrate  tissues  with  the  microscope  to  any  considerable  depth,  but 
are  restricted  to  nearly  a  single  plane.  If  it  were  posssble  to  penetrate 


166 


PRACTICAL   MICROSCOPY. 


with  the  eye  the  entire  thickness  of  the  tendon,  we  might  trace  the 
lymph  paths  or  channels  from  the  abdominal  to  the  thoracic  surface.) 


FIG.  111.— A  SMALL  PORTION  OF  SPECIMEN  SHOWN  IN  FIG.  110,  MORE  HIGHLY  MAGNIFIED,    x  350. 

A,  A,  A.    Large  lymph-channel. 

B.  Valve  in  the  course  of  last. 

C,  C,  C.    Lymph  capillaries  in  the  more  solid  parts  of  the  tendon. 

D.  Pavement  cells  upon  which  a  large  amount  of  silver  has  deposited.    Failure  to  follow  the 
instructions  for  the  staining  frequently  results  in  a  like  deposition  of  silver  over  the  whole  sur- 
face. 


LYMPHATIC    NODES    OK    GLANDS.  167 


LYMPHATIC  NODES  OE  GLANDS. 

At  numerous  points  along  the  course  of  lymphatic  vessels  they  pen- 
etrate small  nodules  of  so-called  adenoid  tissue,  which  have  heen 
termed  lymphatic  glands.  They  are  frequently  microscopic;  others, 
again,  not  unusually  attain  the  size  of  a  large  pea.  They  secrete 
nothing,  hence  are  not  glands.  They  are  somewhat  sponge-like  in 
structure,  and  the  lymph  filters  slowly  through  them. 

Most  frequently  several  ducts  enter  one  of  these  larger  nodes,  while 
perhaps  only  a  single  efferent  will  be  found. 

The  histology  of  a  lymph  node  is  not  always  easily  comprehended 
by  the  student,  and  I  have  endeavored  to  make  a  diagram  (Fig.  112) 
that  would  simplify  the  matter  somewhat.  They  are  enveloped  by  a 
capsule  of  connective  and  involuntary  muscular  tissue,  which  sends 
trabeculm  into  the  body  of  the  organ,  and  these  branching  posts  sup- 
port the  structure  as  a  framework.  The  interstices  are  quite  small  in 
the  more  central  portion  and  larger  toward  the  periphery;  this  has 
resulted  in  the  application  of  the  terms  medullary  and  cortical  to  the 
respective  parts.  The  nutrient  blood-vessels  are  contained  in  the 
framework.  The  compartments  contain  the  structure  peculiar  to  the 
lymphatic  system,  viz.,  adenoid  tissue. 

Adenoid  tissue  consists  of  a  mass  of  flattened  cells,  with  numerous 
delicate  fibrillar  prolongations,  which  branch  and  anastomose  so  as  to 
form  an  interwoven  structure — the  adenoid  reticulum.  Klein  regards 
the  cells  as  forming  no  essential  part  of  the  structure,  but  considers 
them  as  flattened  plates  attached  to  the  fibrils.  The  meshes  of  the 
adenoid  reticulum  are  in  connection  with  the  fibres  of  the  trabeculae 
and,  with  exception  of  the  portion  next  the  latter,  are  filled— crowded, 
in  fact — with  countless  small  spherical  lymphoid  cells.  Those  por- 
tions of  the  tissue  which  contain  the  cells  are  termed  follicular  cords. 

The  lymph  path  is  the  portion  between  the  fibrous  trabeculae  and 
the  follicular  cords. 

When  we  learn  that  the  trabeculae,  follicular  cords,  and  lymph 
paths  each  pursue  very  tortuous  and  branching  routes,  we  can  appre- 
ciate the  complexity  of  the  organ  as  a  whole. 

The  blood-vessel  arrangement  presents  no  anomalies.  The  small 
arterial  trunks  enter  within  the  trabeculae,  finally  break  into  capilla- 
ries which  supply  the  follicular  cords,  etc.,  and  the  blood  is  then  col- 
lected by  the  venules  for  the  efferent  veins. 


168 


PRACTICAL     MICROSCOPY. 


Small  diffuse  collections  of  adenoid  tissue  have  already  been  seen  in 
many  organs.  These  do  not  differ  essentially  from  the  tissue  just 
described,  excepting  that  there  is  no  definite  arrangement  of  trabeculss 
and  lymph  paths,  as  in  the  compound  lymph  node;  the  lymph  simply 
filters  through  the  reticulum,  the  same  being  a  part  of  the  lymph- 
channel  system  of  the  tissue  in  which  the  adenoid  structure  may 
occur. 


FIG.  112.— DIAGRAM.    PERIPHERAL  PORTION  OF  A  LYMPH-NODE. 

A,  A.    Afferent  lymph-vessels. 

B.  Capsule  of  the  node,  with  lymph-spaces  C.  C. 

D,  Trabecula  of  connective  tissue. 

E,  E,  E.    Lymph  path  in  the  node. 

F,  F.    Follicular  cords. 

G,  G,  G.    Lymphoid  cells  in  the  cell -network  of  the  paths. 
H,  H.    Blood  capillaries  of  the  cords. 

The  arrows  show  course  of  lymph. 


SECTION    OF   MESENTERIC    LYMPHATIC    NODE.  169 


PEACTIOAL  DEMONSTRATION. 

The  mesenteric  lymphatic  nodes  present  the  most  typical  structure, 
may  be  obtained  from  the  human  subject,  if  fresh,  although  those 
from  the  dog  are  preferable,  on  account  of  the  better  condition  of  the 
tissue  as  usually  secured. 

The  nodes  should  be  sliced  in  half,  placed  in  Miiller  for  a  week, 
and  then  hardened  by  two  days'  immersion  in  strong  alcohol. 

Sections  should  be  mounted,  of  two  kinds,  viz. :  Those  including 
the  whole  area  of  the  node — which  need  not  be  very  thin — for  demon- 
stration of  the  scheme  or  plan  of  structure,  and  excedingly  thin  ones, 
even  though  they  may  include  only  a  small  part  of  the  organ,  for 
study  of  the  details  of  the  adenoid  reticulum.  The  latter  purpose 
will  be  subserved  by  shaking  a  number  of  thin  cuts  in  a  test-tube 
with  alcohol  for  a  few  minutes,  and  with  considerable  violence,  even 
to  the  sacrificing  of  most  of  the  sections.  The  agitation  will  dislodge 
the  lymph  cells,  which  otherwise  would  obscure  the  histology  of  the 
follicular  cords. 

Stain  deeply  with  haema.  and  eosin,  and  mount  the  thicker  sections 
in  dammar,  and  those  especially  thin  in  glycerin. 

SECTION   OF   MESENTERIC   LYMPHATIC  NODE. 

(Figs.  113  and  114.) 
OBSERVE  : 

(L.) 

1.  The  fibrous  capsule.     (Note  the  elongate  dots  in  the  deeper 
parts  of  the  capsule — the  nuclei  of  the  smooth  muscular  tissue, 
the  thick-walled  arteries,  the  lymph  spaces.) 

2.  The  trabeculae.     (Trace  these  as  they  penetrate  the  organ  and 
observe  that  they  frequently  end  abruptly,    on  account  of   having 
curved,  so  as  to  leave  the  plane  occupied  by  the  section.     The  tra- 
beculse  are  not  partitions,  like  the  iuterlobular  pulmonary  septa  or 
the  prolongations  from  the  capsule  cf  Glisson  in  the  liver;  they  are 
not  unlike  rods  or  posts,  making  a  framework  and  not  producing 
alveoli.     Find  one  divided  transversely.) 

3.  The  follicular  cords.     (They  are  recognized  as  granular  masses 
between  the  trabeculae.     Observe  the  varying  forms,  largest  and 
more   spherical  or  ellipsoidal,   near  the   periphery — cortex.     The 
smaller  ones  of  the  central  region  (medulla)  must  not  be  overlooked, 
as  the  differentiation  is  sufficiently  marked  between  them  and  the 
variously  sectioned  trabeculae.) 

4.  The  lymph  paths.     (These  can  be  appreciated  by  remembering 


170  PRACTICAL   MICROSCOPY. 

that  the  follicular  cords  do  not  entirely  fill  the  spaces  between  the- 
trabeculae,  and  that  the  area  between  the  two,  i.  e.,  outside  the  cords, 
is  the  more  open  in  texture,  and  contains  the  filtering  lymph. 
They  are  more  distinct  in  the  cortex.) 


FIG.  113.—  VERTICAL,  SECTION  OP  A  LYMPH-NODE  FROM  THE  MESENTERY,    x 

A.  Capsule  of  node. 

B.  Lymph  -spaces  in  the  last. 

C.  C.    Trabeculse,  L.  S. 

D.  D.    Follicular  cords,  L.  S. 

E.  Obliquely  sectioned  trabecula. 

F.  F.    Large  blood-vessels  of  the  central  portion  of  the  node. 

G.  Trabecula  in  T.  S. 

H.    Follicular  cord  in  T.  S. 

I.    Small  and  irregular  cords  of  the  centre  of  the  node. 
J.    Obliquely  sectioned  trabecula  of  the  centre  of  the  node. 
K,  K,  K.    Lymph-paths- 


5.  The  histology  of  the  capsule,     (a)  The  closely  united  con- 
nective tissue  with  the  scattering  elastic  fibres  of  the   external 
layer,     (b)  The  smooth  muscle  of  the  deeper  portions,     (c)  Sec- 
tions of  arteries.     (These  may  present  of  considerable  size.)     (d) 
The  lymph  spaces.     (The  differentiation  is  by  the  flattened  endo- 
thelia  of  spaces  which  otherwise  would  be  supposed  mere  rifts  in  the 
tissue,  inasmuch  as  no  definite  or  special  wall  can  be  detected.) 

6.  The  structural  elements  of  the  trabeculse.     (They  are  simi- 
lar to  those  of  the  capsule,  excepting  the  elastic  element,  which  can- 


SECTION    OF   MESENTERIC    LYMPHATIC   NODE. 


171 


not    here    be    demonstrated.     Note  the    variously  sectioned    small 
arteries.) 

7.  The  follicular  cords.  (In  the  thicker  section,  the  field  will  be 
completely  crowded  with  lymphoid  cells.  Select  a  thin  field  and 
observe:  (a)  The  lymphoid  cells.  (These  will  be  found  varying  in 
size  from  a  very  small  red  blood-disc  to  that  of  a  large  white  corpuscle; 
some  are  filled  with  granules  only,  and  others  with  one,  two,  and 
even  three  nuclei.)  (b)  The  branching  endothelioid  cells,  (c)  The 
delicate  fibrillae  of  the  adenoid  reticulum.  (You  may  endeavor  to 


FIG.  114.— FRAGMENT  OP  SECTION  SHOWN  IN  FIG.  113.    MORE  HIGHLY  MAGNIFIED,    x  350 

A.  Trabecula. 

B.  Follicular  cord. 

C.  Lymph-path. 

D.  Large  branching  cells  of  the  path-network. 

E.  Capillaries  of  the  cord. 


determine  whether  this  reticulum  exists  as  an  offshoot  of  the  endothe- 
lioid cells,  or  whether  the  latter  are  simply  adherent  to  the  broadened 
plates  of  the  former.) 

8.  The  reticulum  of  the  lymph  paths.     (Observe  that  this  is  pre- 
cisely like  the  reticulum  of  the  follicular  cords,  as  demonstrable  after 


172  PRACTICAL    MICROSCOPY. 

shaking  out  most  of  the  lymph  corpuscles  of  the  last.)  (a)  The 
connection  between  the  fibrillae  of  the  paths  and  those  of  the 
trabeculae. 

9.  Capillaries  of  the  paths  and  cords.  (These  will  be  recog- 
nizable only  by  the  regular  succession  of  the  contained  red  blood- 
corpuscles.  ) 


THE   SPLEEN.  173 


THE  SPLEEN. 

The  spleen  presents  no  regular  subdivision  of  parts  which  may  be 
studied  separately  and  combined  afterward,  as  we  are  able  to  do 
with  organs  like  the  lung,  liver,  etc.  The  spleen  is  a  ductless  organ 
or  so-called  gland,  and  the  plan  or  scheme  may,  perhaps,  be  best 
comprehended  by  following  the  blood  distribution. 

The  splenic  artery  enters  the  organ,  supported  by  a  considerable 
amount  of  connective  tissue,  and  rapidly  breaks  into  smaller  branches, 
from  which  the  arterioles  leave  at  right  angles.  The  arterioles 
quickly  merge  into  capillaries,  which  form  plexuses  throughout  the 


#ip^ufo 


i£ii* 


%afyl$u^ 
tuft*" 

Artery 


FIG.  115.— DIAGRAM.    SHOWING  THE  COURSE  OF  BLOOD  IN  THE  SPLEEN. 

different  portions  of  the  organ.  Here  we  meet  with  an  anomalous 
structure. 

The  capillaries,  instead  of  uniting  to  form  venules  as  in  the  usual 
vascular  plan,  empty  their  contents  into  small  chambers  or  sponge-UJce 
cavities — the  venous  spaces.  The  blood,  after  filtering  through  these 
venous  interstices,  is  collected  in  larger,  irregular,  vein-like  channels, 
which  finally  conduct  the  blood  into  the  veins  proper  and  out  of  the 
spleen. 

The  tissue,  containing  the  vascular  arrangement  described  in  the 
last  paragraph,  is  called  spleen  pulp. 


174  PRACTICAL   MICROSCOPY. 

The  fibrous  capsule  which  envelopes  the  spleen  sends  trabeculae 
within,  which  form  a  framework;  and  from  this  fibrils  are  sent  off 
which  branch,  broaden,  and  inosculate  to  form  t/ie  venous  chambers  of 
the  pulp. 

The  arteries  are  frequently  surrounded  by  nodules  of  adenoid  tissue, 
sometimes  globular,  more  frequently  considerably  elongated,  and  fol- 
lowing the  vessel  for  a  considerable  distance.  These  nodules  are 
called  Malpighian  bodies.  They  bear  no  resemblance  to  similarly 
named  structures  in  the  kidney,  excepting,  perhaps,  when  seen  in 
transverse  section  by  the  naked  eye. 

The  spleen  will  thus  be  seen  to  consist  of  a  fibrous  trabeculated 
framework,  the  pulp,  blood-vessels,  and  more  or  less  isolated  nodules 
of  adenoid  tissue. 

PKACTICAL   DEMONSTKATION. 

The  organ  must  be  absolutely  free  from  decomposition.  If  human 
tissue  cannot  be  obtained  in  good  condition,  recourse  may  be  had  to 
the  ox,  which  will  provide  an  excellent  substitute.  The  small  super- 
numerary spleens,  not  infrequently  found  during  post-mortem  work, 
are  most  desirable,  as  sections  can  be  easily  made  through  the  entire 
organ. 

Pieces  of  tissue  half  an  inch  cube,  including  a  portion  of  the  cap- 
sule, should  be  hardened  as  directed  for  lymph  nodes.  Sections  are 
easily  made  without  the  microtome,  as  the  mass  is  very  firm;  they 
should  be  thin  and  stained  with  borax-carmine,  and  mounted  in  dam- 
mar or  in  glycerin. 

SECTION  OF  HUMAN  SPLEEN,    CUT  AT   RIGHT  ANGLES 
TO   AND   INCLUDING    THE   CAPSULE.     (Fig.  116.) 

OBSERVE: 


1.  The  fibrous  capsule,     (a)  Its  division  into  two  very  distinct 
portions  or  layers,     (b)  The  clear  translucent  appearance  of  the 
tissue  (elastic)  of  the  outer  layer,     (c)  The  darker  deep  layer  with 
elongate  nuclei.     (The  elastic  element  of  the  capsule  not  infrequently 
becomes,  in  the  human  subject,  considerably  increased;  and  this  de- 
velopment  occurs   irregularly,    sometimes   in   the   form   of   minute 
nodules.     I  do  not  know  that  they  present  any  pathological  signifi- 
cance. ) 

2.  The  trabeculae.     (The  depth  to  which  they  may  be  traced  will 
depend  largely  upon  the  direction  of  the  section.)     (a)  That  these 
are  not  bands,  but  bundles,  more  or  less  circular,  in  transverse  sec- 


SECTION   OF    HUMAN    SPLEEN. 


175 


tion.  (b)  Their  irregular  course,  quickly  after  leaving  the  sur- 
face, (c)  That  occasionally  a  small  artery  may  be  found  within 
them,  though  they  are  usually  destitute  of  large  vessels,  (d]  The 
elongate  nuclei  of  the  muscular  fibre  largely  forming  the  trabeculae. 
3,  The  large  blood-vessels,  (a)  The  arteries  more  frequent 


FIG.  116.    SECTION  OF  THE  SPLEEN.    X  60. 

A.  Elastic  portion  of  the  capsule. 

B.  Lymph  spaces  of  last. 

C.  Involuntary  muscular  portion  of  capsule. 

D.  Deeply  pigmented  portions  of  capsule. 
K,  E.    Trabeculse  from  C. 

F.  Trabeculae  in  oblique  section. 

G,  G.    The  spleen  pulp. 

H,  H.    Large  arteries  in  T.  S. 

I.    Arteries  in  L.  S. 

J.    Adenoid  nodule,  not  connected  with  an  artery. 

K.    A.denoid  nodule.— Malpighian  body— along  course  of  artery. 

L.    Adenoid  nodule  in  T.  S. 

M.    Vein. 

than  veins.     (&)  Their  very  prominent  adventitia.     (c)  Their  tor- 
tuous course. 

4.  The  adenoid  tissue.  (This  you  will  be  enabled  to  recognize 
by  the  great  number  of  lymphoid  cells  of  the  adenoid  structure,  the 
nuclei  of  which  become  stained  very  deeply  blue  with  haema.,  giving 


176  PRACTICAL   MICROSCOPY. 

a  very  distinct  differentiation.  At  this  point,  examine  every  part  of 
the  specimen,  and  endeavor  to  detect  even  the  most  minute  collection 
of  this  tissue.)  (a)  Around  arteries,  constituting  the  so-called  Mal- 
pighian bodies,  (b)  Transverse  sections  of  Malpighian  bod- 
ies, noting  that  the  vessel  is  seldom  in  the  centre  of  the  nodule. 
(c)  Nearly  longitudinal  sections  of  Malpighian  nodules,  observ- 
ing that  the  adenoid  tissue  usually  follows  or  surrounds  the  artery 
for  a  short  distance  only,  (d)  That  the  distribution  is  not  confined 
to  the  arteries,  but  is  quite  common  around  trabeculae  and  beneath 
the  capsule. 

5.  The  Spleen-pulp.     (This  will  be  found  in  those  portions  of  the- 
section  not  occupied  by  structures  previously  demonstrated;  and  will 
be  determined  by  its  light  color.     Keview  the  whole  area,  and  en- 
deavor to  differentiate  every  portion  of  the  adenoid  and  pulp  tissue.. 
The  staining  will  have  been  your  principal  guide  thus  far,  the  pulp- 
elements  appearing  in  strong  contrast  by  their  pink  eosin  color.) 

(H.) 

6.  The  structural    elements   of  the    capsule,     (a)  The  nu- 
merous minute  lymph-spaces  and  the  imperfect  vascular  sup- 
ply,    (b)  The  nuclei  of  the  peritoneal  cell  covering.     (This  pre- 
supposes that  the  section  has  been  selected  so  as  to  include  the  peri- 
toneal investment.)      (c)  The  abundant  and  closely  packed  elastic 
fibrillae.      (d)  The  muscle  nuclei  of  the  deeper  parts,      (e)  Cells 
containing  granular  yellow  pigment.     (The  quantity  varies  largely 
with  different  specimens.) 

7.  The   Malpighian  nodules,     (a)  The  arterioles — very  small 
and  apt  to  escape  attention  unless  filled  with  blood  corpuscles.     (#} 
The  adenoid  reticulum.      (This  will  be  difficult  of  satisfactory 
demonstration,  excepting  the  section  be  thin.) 

8.  The  elements  of  the  pulp,     (a)  Large  flattened  cells,  the- 
branches  forming  the   mesh  work  of   venous  channels.     (These  are 
only  susceptible  of  very  satisfactory  demonstration  in  the  spleen  of 
leucocythcemia.)    (b)  Red  blood-corpuscles.     Very  numerous  and 
often  broken  and  distorted,     (c)  Blood  pigment,     (d)  Lymphoid 
or  white  blood-corpuscles. 


SECTION    OF    THE    THYMUS    BODY.  177 


THYMUS  BODY. 

The  thymus  body  (frequently  and  improperly  called  a  gland)  is  an 
adjunct  to  the  lymphatic  system  of — in  man — foetal  and  infantile 
life ;  disappearing,  by  an  atrophic  process,  at  or  before  the  age  of 
puberty. 

It  is  enveloped  by  a  fibrous  capsule,  partitions  from  which  sub- 
divide the  organ  into  lobes  and  lobules.  The  lobules  are  generally 
subdivided  into  follicles,  which  are  irregularly  sized  and  shaped, 
while  tending  to  an  ovoid  form. 

It  is  in  connection  with  the  general  lymphatic  system  by  peri- 
pheral, afferent  lymph-channels ;  and  by  efferent  vessels  which  emerge 
from  the  hili  of  the  lobes — the  lymph  having  meanwhile  traversed 
the  mesh-like  structure  of  adenoid  tissue  composing  the  follicles. 

The  blood-vascular  system  is  in  the  form  of  a  nutritive  supply; 
the  larger  vessels  occupying  the  fibrous  framework,  and  sending 
branches  into  the  follicles.  The  capillary  plexuses  are  more 
abundant  in  the  peripheral  portion  of  the  follicles.  The  blood  is 
collected  in  the  venous  channels  of  the  central  or  medullary  area, 
and  emerges  from  the  organ  by  the  veins  which  accompany  the 
efferent  lymphatics. 

PRACTICAL  DEMONSTRATION". 

The  organ  should  be  obtained  from  a  still-born  infant,  divided  in 
small  pieces,  and  hardened  rapidly  in  strong  alcohol.  Sections 
may  include  an  entire  lobe,  and  be  stained  with  hgema.  and  eosin. 

SECTION   OE    THE    THYMUS   BODY   FROM   AN   INFANT 
AFTER  DEATH  ON  THE  SIXTEENTH  DAY.    (Fig.  117.) 

OBSERVE: 
(L.) 

1.  The  fibrous  capsule. 

2.  Division    by  prolongations  of    1  into  somewhat  spherical 
lobes. 

3.  Subdivision  of  2  into  lobules. 

4.  Subdivision  of  3  into  follicles.     (Note  that  these  are  not  uni- 
formly outlined  by  the  connective  tissue.) 

12 


178 


PRACTICAL  MICROSCOPY. 


5.  The  subdivision  of  the  follicles  into  an  outer,  deeply-stained! 
cortex,   which  completely  surrounds  a  light  centre,  the  medulla. 

6.  The  larger  lymph-spaces  and  arteries  of  the  capsular  and 
trabecular  tissue. 


FIG,  117.— SECTION  OP  A  PORTION  OF  THE  THYMUS  BODY,  FROM  A  CHILD,  SIXTEEN  DAYS  AFTER 

BIRTH.    X  60. 

A,  A.  Capsule  which  divides  the  organ  into  lobes.   Portions  of  six  lobes  are  visible  in  the  section. 

B,  B.  Lymph-spaces. 

C,  C.  Trabeculae  dividing  the  lobes  into  imperfect  lobules. 

D,  D.  Subdivisions  of  the  last  into  follicles. 

E,  E.  Central  light  portion  of  the  lobules. 

(H.) 

7.  The    cortex    of   the    follicles.      (a)   The  numerous  deeply- 
stained    lymph-corpuscles,      (b)   The  network   of    the    adenoid 
tissue.     (This  will  be  greatly  obscured  by  the  lymphoid  cells.)     (c) 
The  blood  capillaries.      Only  recognized  by   the   contained  cor- 
puscles,    (d)  Minute  trabeculae  of  connective  tissue  projected  from 
the  capsule. 

8.  The  medulla  of  the  follicles,     (a)  The  sparsity  of  lymph- 
corpuscles  as  compared  with  the   cortical   portions,     (b)   Large 


SECTION    OF    THE    THYMTJS    BODY.  179 

mono  nucleated  cells,      (c)  Still  larger  multinucleated  cells. 

(d)  Larger — though  varying  in  size — spherical  bodies,  Hassall's 
corpuscles.  (These  are  composed  of  epithelioid  cells,  arranged  con- 
centrically, and  are  unlike  any  other  structure  found  in  the  normal 
tissues  of  the  body.  They  resemble  very  closely  the  smaller  "  brood 
nests  "  of  epithelial  cancer. )  (e)  Small  thin- walled  venules. 


180  PRACTICAL    MICROSCOPY. 


THE  NERVOUS  SYSTEM, 

STRUCTURAL  ELEMENTS. 

The  elements  of  the  nervous  system  are  : 

1.  Nerve  Fibres. 

2.  Nerve  Cells. 

3.  Connective  Tissue. 

4.  Peripheral  Termini. 

i 

NERVE    FIBRES. 

A  typical  nerve  fibre  consists  of  three  portions,  viz.:  a  central 
conducting  portion,  the  axis  cylinder ;  the  medullary  sheath,  or 
white  substance  of  Scliwann ;  and  the  enveloping  connective-tissue 
substance,  the  neurilemma.  This  constitutes  a  medullated  nerve- 
fibre,  and  is  found  largely  in  the  trunks  of  the  cerebro-spinal 


FIG.  118.— SEPARATED  NERVE  FIBRES.    X  400. 

A.  Neurilemma  of  a  fibre. 

B.  White  substance  of  Schwann,  stained  with  osmic  acid,  which  hides  the  axis  cylinder. 

C.  Nucleus  of  the  neurilemma. 

D.  One  of  Ranvier's  nodes  in  an  osmic  acid  stained  fibre  showing  the  axis  cylinder  between 
the  separated  portions  of  Schwann's  sheath. 

E.  A  medullated  fibre,  teased  in  normal  salt  solution.    The  medullary  substance  has  be- 
come coagulated  on  exposure  and  removal.    The  axis  cylinder  is  faintly  seen. 

F.  Axis  cylinder  at  torn  extremity. 

G.  Non-medullated  fibre. 

H.    Fibres  without  neurilemma.    Small  clusters  of  medullated  substance  are  seen  covering 
the  axis  at  irregular  intervals. 


NERVE    CELLS.  181 

system.  The  trunks  of  the  sympathetic  system  are  composed  prin- 
cipally of  fibres  destitute  of  the  white  substance  of  Schwann — non- 
medullated  nerves ;  while  fibres  minus  the  neurilemma  exist  in  the 
trunks  belonging  to  some  organs  of  special  sense. 

After  treatment  with  reagents,  the  axis  cylinder  (one-two  thousand 
five  hundredth  to  one-fifteen  thousandth  of  an  inch)  may  be  split  up 
longitudinally,  and  is  found  to  be  composed  of  fine  (one-twenty-five 
thousandth  of  an  inch)  primitive  or  ultimate  fibrillae,  which  present 
minute  varicosities  or  swellings  at  irregular  intervals. 

The  white  substance  of  Schwann  presents  under  the  microscope  the 
most  prominent  feature  of  medullated  nerves,  affording  a  nearly  com- 
plete investment  of  the  nerve  axis. 

The  neurilemma  is  an  elastic  connective-tissue  envelope,  which 
completely  invests  the  medullary  substance.  This  tubular  membrane 
is  nucleated,  and  at  irregular  intervals  is  constricted  so  as  to  reach 
very  nearly  the  axis  cylinder.  These  constrictions  are  called  by  Ran- 
vier  nodes,  and  it  is  believed  that  the  perineurium  presents  a  single 
nucleus  between  each  of  these  nodal  points.  The  constrictions  do 
not,  however,  affect  the  even  calibre  or  continuity  of  the  axis  cylin- 
der. 

A  typical  nerve  fibril  has  been  described  as  resembling,  structu- 
rally, a  doubly  insulated  telegraphic  cable,  but  the  comparison  is  un- 
fortunate and  misleading,  as  the  functioning  of  the  nerve  bears  no- 
resemblance  to  the  phenomena  exhibited  by  electrical  conductors. 


NERVE   CELLS. 

Nerve  cells  are  usually  grouped,  and  are  the  essential  feature  of 
nerve  centres,  otherwise  called  ganglia  or  gray  matter.  Ganglion 
cells  are  among  the  largest  cell  elements  of  the  body,  and  consist  of  a 
dense,  reticulated,  and  frequently  pigmented  ground  work,  inclosing 
a  large  translucent  nucleus,  and  usually  a  single  nucleolus.  One  or 
more  prolongations,  poles  or  horns,  are  sent  from  these  cells,  and 
hence  they  have  been  classified  as  unipolar,  bipolar,  tripolar,  quadri- 
polar,  and  multipolar,  according  to  the  number  of  projections.  The 
cell  prolongations  generally  divide  soon  after  leaving  the  body,  and 
subdivision  continues  until  exceedingly  minute  fibrils  result,  which 
serve  as  connecting  links  of  the  elements  of  a  ganglion.  Usually  one 
(the  larger)  pole  is  projected  which  remains  unbranched.  This  be- 
comes the  axis  cylinder  of  a  nerve  fibril,  and  affords  connection 
between  the  elements  of  a  ganglionic  centre  and  the  conducting  por- 
tion of  the  nervous  apparatus. 


182  PRACTICAL   MICROSCOPY. 

Ganglion  cells   are  surrounded  by  irregular  channels  or  lymph- 
spaces,  and  are  thus  in  intimate  relation  with  the  lymphatic  system. 


CONNECTIVE   TISSUE   OF    THE   NERVOUS   SYSTEM. 

The  connective  tissue,  which  serves  to  unite  the  elements  of  a  nerve 
trunk,  does  not  differ  materially  from  the  susteutacular  tissue  of  other 
organs.  Different  terms  are  applied,  according  to  its  use  and  loca- 
tion, as  follows: 

EPINEURIUM. — Forming  the  sheath  of  the  entire  nerve  trunk. 

PERINEURIUM. — Surrounding  the  bundles  composing  the  nerve 
trunk. 

ENDONEURIUM. — Permeating  and  uniting  the  elements  of  the  bun- 
dles. 


Fia.  119.— TRANSVERSE  SECTION  OP  THE  A.NTERIOR  CRURAL  NERVE.    X  250. 

A.  The  epineurium. 

B.  Adipose  tissue  in  the  loose  areolar  tissue  of  the  sheath. 

C.  Lymph-spaces  of  the  epineurium. 

D.  Large  blood-vessels  of  epineurial  sheath. 

E.  Perineurium  surrounding  nerve  bundles. 

F.  Lymph-spaces  of  last. 

G.  Medullated  nerves  in  T.  S.  supported  by  connective  tissue— endoneurium. 


NELTKOGLIA. 


183 


NEURILEMMA. — Surrounding  the  individual  nerve  fibres  of  a  bun- 
dle. 

The  formula  E.  P.  E.  N.,  composed  of  the  initial  of  the  name  of 
the  investments  from  without  inward,  will  aid  the  memory. 

The  epineurium  serves  to  protect  the  organ  in  its  passage,  and  to 
support  the  nutrient  blood-vessels  and  the  channels  of  lymphatics. 
The  fibres  run  both  longitudinally  and  transversely.  The  perineu- 
rium,  arranged  in  dense  bands,  forms  distinct  sheaths  for  the  nerve 
bundles,  the  fibres  running,  for  the  most  part,  circularly.  The  endo- 
neurium  not  infrequently  divides  the  nerve  bundles  into  smaller  or 
primitive  bundles.  It  supports  the  blood  capillaries,  contains  small 
lymph-spaces,  and  its  nuclei  are  frequently  large  and  prominent. 

The  final  distribution  of  the  elements  of  a  nerve  trunk  is  effected 
by  subdivision;  first,  of  the  large,  and  afterward  of  the  primitive 
bundles  or  fasciculae.  The  perineurial  sheaths  are  prolonged,  fur- 
nishing the  dividing  bundles,  even  to  the  final  distribution,  where, 
.around  terminal  and  single  medullated  fibres,  the  sheath  remains  as 
a  layer  of  exceedingly  delicate  flattened  cells.  The  necessity  for  the 
endoneurium  ceases  with  the  ultimate  subdivision  of  the  nerve  fas- 
ciculus. 

NEUROGLIA. 

The  sustentacular  or  supporting  tissue  of  the  brain  and  spinal  cord 
differs  materially  from  ordinary  connective  tissue.  It  presents  an 


FIG.  120. — NEUROGLTA,  FROM  BENEATH  THE  PIA  MATER  OF  THE  SPINAL  CORD. 

A.  Network  of  neuroglia  fibrils. 

B.  Spider  (Deiter's)  cells. 

C.  Nerve  fibres  in  T.  S. 


X400. 


184  PRACTICAL    MICROSCOPY. 

interlacement  of  fibres  which,  even  with  the  highest  powers  of  the- 
microscope,  appear  ,of  exceeding  tenuity.  The  neuroglia  mesh  sup- 
ports the  nervous  elements,  scattering  branched  (Deiter's)  cells,  and 
small  round  cells. 

Peripheral  Termini.  (The  demonstration  of  peripheral  nerve 
apparatus  should  not  be  attempted  until  additional  work,  in  the  lines 
hereafter  indicated,  has  secured  for  the  student  a  degree  of  perfection 
in  technique  which  he  is  not  at  present  supposed  to  possess. ) 


SPINAL   COED. 


185- 


SPINAL  COED. 

The  membranes  covering  the  cord  will  be  discussed  later. 

The  spinal  cord  is  composed  of  gray  (cellular)  and  white  (fibrous) 
nerve  matter,  and  serves  as  a  medium  of  communication  between  the 
brain  and  peripheral  nerve  apparatus.  The  arrangement  of  its  sev- 
eral parts  will  be  best  understood  by  the  study  of  a  transverse  section,, 
of  which  Fig.  121  is  a  diagrammatic  representation. 

The  gray  substance  occupies  the  central  portions  of  the  structure,. 


FIG.  121.— DIAGRAM.    CERVICAL  SPINAL  CORD  IN  TRANSVERSE  SECTION. 

A.  Anterior  median  fissure. 

B.  Posterior  median  fissure. 

C.  Anterior  cornu— gray  substance. 

D.  Posterior  gray  cornu. 

E.  Point  of  emergence  of  anterior  root  of  spinal  nerve. 

F.  Posterior  root  of  spinal  nerve. 

G.  White  commissure. 

H.  Anterior  gray  commissure. 
I.  Posterior  gray  commissure. 
J.  Substantia  gelatinosa. 

The  tracts  which  are  named  on  the  diagram  have  no  definite  boundaries  histologically. 
They  are  physiological  areas. 


186  PRACTICAL    MICROSCOPY. 

and  consists  of  two  lateral  masses  and  a  connecting  link  or  commis- 
sure. Near  the  central  portion  of  the  figure,  a  small  circular  opening 
presents — the  transversely  divided  central  canal.  This  is  in  commu- 
nication, in  the  medulla,  with  the  fourth  ventricle,  and  will  serve  as 
a  starting-point  for  our  study. 

The  gray  matter  completely  surrounds  the  central  canal,  and  its 
outline  resembles  the  capital  H.  The  bars  or  columns  each  present 
anteriorly  a  blunted  extremity,  horn  or  cornu,  while  the  posterior 
cornua  are  pointed.  The  lateral  bars  or  columns  are  connected,  as 
we  have  seen,  a  portion  of  the  connecting  substance  passing  in  front 
and  a  portion  behind  the  central  canal — the  anterior  and  posterior 
gray  commissural  lands. 

The  white  substance  is  divided  anteriorly  by  the  anterior  median 
jissure,  which  sections  the  cord  nearly,  but  not  entirely,  to  the  ante- 
rior gray  commissure.  A  corresponding  division  appears  posteriorly 
(the  posterior  median -fissure)  which  does  not  divide  the  cord  posteri- 
orly as  completely  as  does  the  previously  named  fissure  anteriorly; 
but  the  divison  is  indicated  by  a  band  of  neuroglia,  which  penetrates 
entirely  to  the  posterior  gray  commissure.  The  two  masses  of  white 
substance  thus  indicated  by  more  or  less  complete  central  division  are 
termed  lateral  white  columns,  and  these  are  united  just  in  front  of 
the  anterior  gray  commissure  by  white  nerve  tissue— the  white  com- 
missure. The  spinal  nerves  take,  origin  from  the  gray  cornua,  the 
anterior  roots  from  the  anterior  and  the  posterior  roots  from  the  pos- 
terior cornua.  The  white  substance  consists  essentially  of  medullated 
fibres  which,  with  the  exception  of  the  anterior  spiral  nerve  roots  and 
the  commissural  fibres,  pass  mainly  in  a  longitudinal  direction. 

PRACTICAL  DEMONSTRATION. 

Nerve  tissue  should,  under  all  circumstances,  be  hardened  in 
Miiller's  fluid.  The  cord  should  be  obtained  as  nearly  fresh  and  un- 
injured as  possible;  cut  transversely  with  a  sharp  razor  into  pieces 
half  an  inch  long,  and  placed  immediately  in  the  fluid — in  the  pro- 
portion of  a  pint  of  the  mixture  to  two  ounces  of  tissue  The  solution 
should  be  thrown  away  after  twenty-four  hours,  and  a  fresh  supply 
provided.  It  should  be  again  changed  after  three  days,  and  again  after 
another  week.  After  four  weeks  the  bichromate  should  be  poured  off, 
and  the  tissue  rinsed  once  with  water;  after  which  the  hardening  is  to 
be  completed  with  alcohol  in  the  ordinary  manner,  i.  e.,  commencing 
with  the  weak  spirit. 

After  hardening,  pieces  from  the  different  regions  should  be  cut, 
and  this  is  best  effected  by  the  infiltration  methods.  Transverse 
.sections  are  the  most  instructive,  although  the  student  should  after- 
ward study  longitudinal  cuts.  The  sections  must  be  thin,  but  not 


HUMAN    SPINAL    CORD.  187 

necessarily  large,  and  they  may  be  stained  by  the  method  of  Weigert, 
or  with  haema.  and  eosin.  Weigert's  method  requires  very  careful 
manipulation,  and  is  of  more  special  value  in  pathological  research. 

If  human  tissue  cannot  always  be  procured  in  suitable  condition, 
the  cord  of  the  ox,  pig,  sheep,  cat,  or  rabbit  will  serve  well.  The  ox, 
especially,  provides  a  means  of  securing  tissue  of  surpassing  excellence, 
particularly  for  demonstration  of  the  ganglion  cells.  The  cord  of  the 
smaller  domestic  animals  is,  in  nearly  every  respect,  as  valuable  for 
study  as  that  of  man,  especially  as  the  latter  cannot  usually  be  gotten 
before  the  serious  putrefactive  changes,  to  which  nerve  tissue  is  prone, 
have  made  marked  progress. 


HUMAN   SPINAL   COED.     CERVICAL  REGION. 

TRANSVERSE   SECTION.       (Fig.  122.) 

OBSERVE: 
(L.) 

1.  General  arrangement  of  gray  and  white  substance,  with 
the  latter  surrounding  the  former,  which   resembles  in  outline  the 
letter  H. 

2.  Subdivisions  of  white  substance,     (a)  Anterior  median  fis- 
sure.    (Note  its  passage  inward  and  its  cessation  before  reaching  the 
gray  substance.)  (b)  Posterior  median  fissure.  (Note  its  shallowness 
as  a  true  fissure,  and  the  extension  of  the  connective  tissue  from  the 
bottom  inward,  until  the  gray  substance  is  met.     Compare  the  two 
median  fissures.)     (c)  The  emergence  of  the  anterior  nerve-roots. 
(This  provides  the   external   or  lateral   boundary  of  anterior  white 
columns  or  direct  pyramidal   tracts,  the  internal  boundaries  being 
provided  by  the  anterior  median  fissure.)     (d)  The  lateral  columns. 
(These  contain  the  fibres  of  the  crossed  pyramidal  tract,  and  include 
the  white  substance  between  the  anterior  nerve-roots  and  the  posterior 
gray  cornu.     Each  lateral  column  contains  nerve  fibres  which  pass  to 
the  cerebellum — direct  cerebellar  tract;  observe  that  these  tracts  have 
no  internal  histological  boundary.     Note  the  numerous  prolongations 
of  the  pia  mater  inward  in  the  lateral  columns.)     (e)  The  postero- 
internal   or  column  of  Goll — -funiculus  graoilis.     (These  columns 
present  on  either  side  of  the  posterior  median  fissure,  and  are  bounded 
laterally  by  a  prolongation  from  the  pia  mater.)     (/)  The  postero- 
external  columns — -funiculus  cuneatus.     (Bounded  internally  by 
the   postero-internal  columns,  and  externally  by  the  posterior  gray 
cornua.)     (g)  The  white  commissure.     (Note  the  absence  of  a  white 
commissure  posteriorly,  the  posterior   median  septum  reaching  the 
.gray  substance.) 


188 


PRACTICAL   MICROSCOPY. 


3.  Subdivisions  of  the  gray  substance,    (a)  The  central  canal. 

(Should  the  section  have  been  taken  from  the  extreme  lower  cervical 
cord,  this  canal  as  such  will  be  difficult  of  demonstration,  a  number 
of  deeply  stained  cells  only  remaining.)  (b)  The  gray  commissure, 
anterior  and  posterior,  (c)  The  gray  columns,  (d)  The  anterior 
gray  cornua,  broad  and  not  reaching  the  periphery  of  the  cord  sec- 
tion, (e)  The  posterior  cornua,  narrow  and  passing  completely  out, 
posteriorly,  to  form  the  posterior  root  of  a  spinal  nerve. 


FIG.  122.— TRANSVERSE  SECTION  OF  THE  SPINAL  CORD.    MIDDLE  CERVICAL  REGION.    X  60. 

A.    Anterior.  B.    Posterior. 

The  references  in  Fig.  131  apply  also  to  this  illustration.    Also  vide  text. 
This  section  was  made  from  the  cord  of  a  man  who  died  at  the  age  of  75  years,  from  senile 
dementia.    The  gray  substance  is  perfectly  normal,  but  of  somewhat  diminished  area. 

(H.) 

4.  The  white  substance  (select  a  field,  e.  g.,  in  the  anterior 
median  column,  and  observe  the  transversely  divided  nerves),  (a) 
The  nerves  are  not  collected  into  fasciculae,  but  each  fibre  pursues 
an  independent  course,  (b)  The  axis  cylinders,  stained  lightly 
with  the  eosin.  (Note  the  great  variation  in  size. )  (c)  Most  of  the 
axis  cylinders  surrounded  by  more  or  less  concentric  rings  of  translu- 


HUMAN    SPINAL    COED. 


189 


cent,  unstained  white  substance  of  Schwann.  (These  are  medul- 
lated  fibres.)  (d)  The  few  and  scattering  axis  cylinders  without 
surrounding  white  substance.  (Non-medullated  nerves.)  (e)  The 
neurilemma,  appearing  as  a  thin,  violet  ring  around  the  white  sub- 
stance of  Schwann.  (Most  medullated  nerves  of  the  cerebro-spinal 
.system  are  provided  with  this  sheath.)  (/)  The  small,  about  one- 
three  thousandth  of  an  inch,  deeply  haema.  -stained  cells  of  the 
neuroglia.  (g)  The  neuroglia  substance,  finely  granular  or 
fibrillated,  between  the  nerve  fibres,  (h)  The  spider  cells  (Deiter's) 
of  the  neuroglia.  (These  are  not  numerous,  but  easily  found  near  the 
periphery.)  (i)  The  longitudinal  nerve  fibres  passing  from  the  an- 


FIG.  123.— SAME  SPECIMEN  AS  SHOWN  IN  FIG.  122.    MORE  HIGHLY  MAGNIFIED.    REGION  OF  AN- 
TERIOR CORNU.    x  350. 

A.  Medullated  filaments  passing  out  from  the  gray  substance  to  form  the  anterior  root  of 
a  spinal  nerve. 

B.  Ganglion  cells. 

C.  Neuroglia  nuclei. 

D.  Blood-vessels. 

E.  One  of  the  transversely  divided  medullated  fibres  of  the  white  substance,  anteriorly  to 
the  anterior  gray  cornu.    The  line  leads  to  the  neurilemma. 

F.  White  substance  of  Schwann — of  last. 

G.  The  axis  cylinder  of  E. 

terior  gray  cornu  to  form  the  anterior  root  of  a  spinal  nerve,  (j)  The 
different  size  of  the  nerve  fibres  in  different  areas  of  the  section. 
(Note  the  small  fibres  of  the  postero-internal  column.)  (k)  The 
blood-vessels.  (These  vessels  are  largely  confined  to  the  neuroglia- 
septa,  which  pass  in  from  the  pia.  These  septa  contribute  to  the 


190  PRACTICAL    MICROSCOPY. 

formation  of  the  nearest  approach  afforded  by  the  cord  of  nerve 
bundles.) 

5.  The  gray  substance,  (a)  The  central  canal.  (The  canal  is 
lined  with  columnar  ciliated  cells  in  single  layer.  The  cilia  are  rarely 
demonstrable  in  the  human  cord,  on  account  of  changes  which  occur 
very  quickly  after  death.  The  canal  is  usually  broadest  in  its  lateral 
diameter,  viz.,  at  upper  portion  of  cervical  region,  from  one-one 
hundredth  to  one-two  hundredth  of  an  inch,  (b)  The  ground  sub- 
stance. (This  consists,  1st,  of  exceedingly  minute  fibres,  formed  by 
the  repeated  subdivision  of  the  axis  cylinders — the  primitive  fibrillae  ; 
2d,  of  the  delicate  neuroglia  fibres.  It  is  usually  difficult  in  a 
section  to  differentiate  between  the  two.  Attempts  have  been  made, 
with  more  or  less  success,  to  differentiate  by  means  of  staining  agents.) 
(c)  Large  ganglion  cells.  (Select  a  field  in  the  anterior  horn. 
The  straight,  unbranching  axis-cylinder  process  can  frequently  be 
distinguished.  Note  the  large,  shining  nucleus  and  the  deeply  stained 
nucleolus.  These  cells  are  frequently  deeply  pigmented.)  (d)  Small 
ganglion  cells.  (Best  seen  in  the  posterior  horn.  In  the  dorsal 
cord  a  collection  of  medium-sized  cells  presents,  just  within  the  poste- 
rior commissure  and  encroaching  upon  the  white  substance  posteriorly 
to  this,  the  column  of  Lockhart  Clarke.)  (e)  Lymph  spaces.  (Ob- 
served as  a  somewhat  clear  space  around  the  ganglion  cells.)  (f) 
Blood-vessels.  (These  are  much  more  numerous  here  than  in  the 
white  portion;  and  arteries  may  frequently  be  found  of  considerable 
size.)  (g)  Peri-vascular  lymphatics.  (Find  an  artery  in  trans- 
verse section,  and  observe  the  clear  space  around  it,  which  may  be 
mistaken  for  the  result  of  contraction  of  the  tissue  in  hardening. 
Careful  study  will  reveal  minute  branches  of  cells,  passing  between 
the  adventitia  of  the  blood-vessel  and  the  wall  of  the  lymph  space.) 


THE    BRAIN    AND    ITS    MEMBRANES.  191 


THE  BRAIN  AND  ITS  MEMBRANES. 

The  brain  and  spinal  cord  are  surrounded  by  three  connective- 
tissue  layers — the  dura  mater,  arachnoid,  and  the  pia  mater. 

The  dura  is  the  most  external  and  the  thickest  of  the  three  mem- 
branes, and  constitutes  the  periosteal  lining  of  the  cranial  and  spinal 
cavities.  It  consists  largely  of  elastic  tissue,  the  laminae  and  blood- 
vessels of  which  are  supported  by  connective  tissue.  The  outer  sur- 
face is  in  more  or  less  intimate  connection  with  the  bone,  and  both 
surfaces  are  covered  with  a  single  layer  of  thin  pavement  cells. 
Beneath  is  a  space — the  subdural — containing  lymph. 

The  arachnoid,  exceedingly  thin,  presents  an  outer,  glistening, 
pavement-cell  covered  surface  (isolated  from  the  dura  by  the  sub- 
dural space),  from  the  under  (inner)  side  of  which  short  fibrous 
trabeculae  are  projected  to  the  pia.  The  subarachnoidal  space  is 
thus  seen  to  consist  of  numerous  communicating  chambers,  and  these 
spaces  are  everywhere  lined  with  flat  cells,  and  contain  lymph,  as  does 
the  subdural  space. 

The  pia  mater  consists  of  fibrillated  connective  tissue,  usually  in 
intimate  connection  with  the  arachnoid  externally,  by  means  of  the 
trabeculae  of  the  latter.  The  pia  is  exceedingly  vascular,  and  every- 
where covers  the  brain  and  cord,  and,  unlike  the  arachnoid,  pene- 
trates the  sulci  of  the  former  and  the  fissures  of  the  latter,  becoming 
continuous  with  the  neuroglia  tissue. 

The  subdural  and  subarachnoidal  spaces  are  lymph-cavities,  and, 
while  not  in  direct  connection  one  with  the  other,  belong  to  the 
general  lymphatic  system,  and  are  in  eventual  connection.  The  two 
spaces  are  projected,  independently,  in  the  sheaths  of  the  cranial  and 
spinal  nerves — the  subdural  communicating  with  the  lymph  channels 
of  the  epineurium,  and  the  subarachnoidal  with  those  of  the  peri- 
neurium. 

The  arrangement  of  gray  and  white  nerve  substance  in  the  brain  is 
precisely  the  reverse  of  that  of  the  cord.  The  gray  matter  forms  an 
external  covering  or  layer  of  varying  thickness,  while  the  white  matter 
occupies  the  more  central  regions.  Collections  of  gray  matter — gang- 
lia— are  also  situate  in  the  deeper  parts  of  the  brain  substance,  the 
study  of  which  does  not  come  within  the  limits  of  this  work. 

The  brain  substance  does  not  differ,  essentially,  from  the  cord, 
except  in  the  arrangement  of  its  parts.  The  nerve  fibres  are  largely 


192  PRACTICAL   MICROSCOPY. 

medullated,  but  have  no  neurilemma.  The  neuroglia  and  ganglionic 
tissues  do  not  here  differ  in  structure  from  that  previously  de- 
scribed. The  gray  substance  is  arranged  in  layers,  which  are,  in 
.some  instances,  quite  sharply  defined,  and  again  demonstrable  only 
with  considerable  difficulty. 

PRACTICAL  DEMONSTRATION. 

The  tissue  is  to  be  prepared  in  the  manner  usual  with  nerve  sub- 
stance —  hardened  with  Miiller,  followed  by  alcohol.  Thin  sections, 
stained  deeply  with  haema.  and  eosin,  may  be  mounted  in  dammar  or, 
if  preferred,  in  glycerin. 

SECTION   OF   HUMAN   CEREBRUM.      CUT   PERPENDICU- 
LARLY TO   THE   SURFACE.     (Fig.  124.) 

OBSERVE: 


1.  The  membranes.     (In  the  drawing  only  the  arachnoid  and  pia 
are    shown.)     (a)  The    fine    fibrillar    mesh  of  the    arachnoid. 
(b)  The  nuclei  of  the  flattened  cell-covering,     (c)   The  large 
blood-vessels,    (d)  The  pia.   (e)  Its  continuity  with  the  neuro- 
glia of  the  cerebrum. 

2.  The  outer  layer  —  the  first  —  of  the  gray  substance.    (This  layer 
is  poorly  defined,  but  can  usually  be  made  out.    It  consists  of  primitive 
nerve  fibrillae,  neuroglia  fibrils,  and  scattered  spherical  cells.) 

3.  The  second  layer.     (This  layer  presents  about  the  same  thick- 
ness as  the  preceding,  and  will  be  recognized  by  the  numerous  small, 
triangular  nerve-cells.     Indeed,  these  afford  the  only  means  of  dis- 
tinguishing the  boundary  between  the  two  layers,  as  the  stained  ele- 
ments of  the  outer  layer  are  seldom  pyramidal.) 

4.  The  third  layer.     (This  layer  —  the  thickest  of  all  the  gray 
laminae  —  has  been  shortened  in  the  drawing,  on  account  of  lack  of 
space.     It  is  three  or  four  times  as  thick  as  the  first  layer,  and  will  be 
readily  made  out  by  the  large,  elongate,  pyramidal  cells,  with  their 
long  axes  at  right  angles  to  the  brain  surface.     Medullated  fibres,  in 
more  or  less  distinct  bundles,  pass  between  the  column-like  ganglion 
cells.) 

5.  The  fourth  layer.     (The  large  cells  of  the  third  layer  are  seen 
to  stop  abruptly,  as  we  pass  inward,  and  give  place  to  small,  triangular 
nerve-cells.    This  brings  us  to  the  fourth  plane.    Between  the  cells  of 
this  layer,  bundles  of  nerve-fibres  are  seen,  as  they  radiate  toward  the 
cerebral  surface.) 


THE    BRAIN    AND    ITS   MEMBRANES. 


198 


6.  The  fifth  layer.     The  line  of  demarcation  between  this  and  the 
fourth  layer  is  feebly  shown;  but,  on  close  attention,  it  will  be  ob- 
served that  the  small  cells  of  the  fourth  layer  rather  abruptly  give 
place  to  elongate  ones,  not  unlike  those  of  the  third  stratum.     The 
nerve-bundles  are  here  more  plainly  indicated. 

7.  The  white  matter.    (The  ganglion  cells  here  cease,  and  the  field 
is  occupied  with  medullated  fibres  and  neuroglia,  the  spherical  nuclei 
of  the  latter  becoming  prominent  from  the  deep  haema.  staining.) 


FIG.  134.— VERTICAL  SECTION  OF  CEREBRAL  CORTEX.  SUPERIOR  FRONTAL  CONVOLUTIO  N.  X  250. 

A.  Arachnoid. 

B.  Pia  mater. 

C.  D,  E,  F,  G.    First,  second^third,  fourth,  and  fifth  layers  of  gray  matter. 
H.    White  brain  substance. 

8.  The  nutrient  blood-vessels.  (The  capillaries  projected  from 
the  pia  are  especially  to  be  noticed,  often  of  the  diameter  of  a  single 
blood-corpuscle,  and  presenting  as  branching  lines,  composed  of  these 
elements— indeed  difficult  of  demonstration  when  empty.  Note  the 
light,  perivascular  lymph-spaces,  well  seen  around  the  larger  arteries  in 
transverse  section.) 
13 


194:  PRACTICAL    MICROSCOPY. 

VERTICAL    SECTION    OF  HUMAN    CEREBELLUM.      PRE 
PARED    AS    LAST    SPECIMEN.     (Figs.  125  and  126.) 

OBSERVE  : 


1.  The  arrangement  of  the  cortex  in  the  form  of  leaflets. 

2.  The  extension  of  the  gray  laminae  within  even  the  minutest 
folds  of  the  leaves,  so  as  to  completely  envelop  the  central  white  nerve- 


FIG.  125.— LONGITUDINAL  SECTION  OP  ONE  OF  THE  FOLIA  OF  THE  CEREBELLUM.     X  60. 

A,  A.    Line  of  pia  mater. 

B,  B.    Sulci. 

C,  C.    Outer  layer  of  gray  matter. 

D,  D.    Inner  layer  of  gray  matter,  including  Purkinje's  cells. 

E,  White  nerve  substance. 

substance.  (The  staining  has  heen  so  selected  by  the  tissue  as  to 
divide  the  outer  gray  matter  into  two  prominent  layers.  The  ex- 
planation of  this  will  follow  increased  amplification.) 

3.  The  central  white  matter.     (The  fibrillar  character  can  be 
made  out,  and  the  general  plan  seen  to  consist,  as  in  the  cerebrum,  of 


VERTICAL    SECTION   OF    HUMAN   CEREBELLUM. 


195 


central  nerve  fibrillae  radiating  toward  the  cells  of  the  cortical  gray 
substance.) 


4.  The  outer  gray  layer.  (This  is  the  thickest  of  the  three  layers. 
The  prominent  elements  to  be  observed  are  :  the  scattering  spheri- 
cal neuroglia  and  small  nerve-cells,  nerve-fibrils  passing  at  right 
angles  to  the  surface  and  lost  as  the  outer  region  is  approached,  the 
prominent  blood-vessels  which  pass  in  from  the  pial  investment.) 


FIG.  126.— VERTICAL  SECTION,  CORTEX  OF  CEREBELLUM.    PORTION  OP  SECTION  SHOWN  IN  FIG.  125, 
MORE  HIGHLY  MAGNIFIED,     x  250. 

A.  Outer  layer  of  gray  matter. 

B.  Layer  of  Purkinje's  cells. 
G.    Inner  gray  layer. 

D.    White  nerve  substance. 

5.  The  ganglionic  layer.  (Directly  beneath  the  outer  layer  the 
section  becomes  deeply  stained,  from  the  presence  of  numerous  small 
cells,  among  and  partly  concealed  by  which  are  the  large  ganglion 
cells  of  Purkinje.  These  are  flask-shaped,  and  are  arranged  in  a 
single  plane,  with  their  long  axes  vertically.  A  thread-like  prolon- 


196  PRACTICAL    MICROSCOPY. 

gation  may  be  seen  penetrating  the  layer  beneath,  providing  the  cell 
has  been  centrally  sectioned.  Large  horns  are  projected  from  the 
outer  extremity  of  the  cells,  branches  from  which  provide  the 
nerve-fibrils  seen  in  the  last-observed  layer.  The  cell  bodies  take  the- 
eosin,  and  the  nuclei  the  logwood.) 

6.  The  granular  layer.    (This  is  the  layer  seen  so  distinctly  with 
the  low  power.     It  consists  of  innumerable   small,    deeply  hsema.- 
stained  bodies,  usually  spherical,   which  are,  as  is  believed,  mostly 
neuroglia  cells.     These  nucleated  elements  are  embedded  in  an  ex- 
ceedingly fine  matrix  of  neuroglia  [Klein]  fibrils.    Search  carefully 
for  the  axis  cylinder  processes  of  the  Purkinje  cells  which  pierce 
this  layer,  and  follow  them  into  the  white  matter  below.) 

7.  The  white   subtahce.     (This   consists  of  medullated  nerves 
which  arise  largely  from  the  cells  of  the  second  gray  layer.     Klein  has 
also  traced  fibres  into  the  nuclear  layer,  and  demonstrated  their  dis- 
tribution to  the  small  ganglion  cells  of  the  lamina,  and  to  the  network 
of  the  outer  gray  substance.) 


FORMULAE.  197 


MISCELLANEOUS  FORMULAE. 

DAMMAR    MOUNTING  VARNISH. 

No.  1. 

Gum  Dammar, 4  ounces. 

Gum  Mastic  (in  "tears"),     ...  2       "  ' 

Spirits  of  Turpentine,        ....  8      " 

Chloroform  (Squibb's),  ....  4       " 

Mix  the  dammar  with  about  an  equal  bulk  of  clean  broken  glass. 
Put  in  a  wide-mouth  bottle,  and,  having  added  the  turpentine,  set  in 
a  warm  place.  The  glass  is  added  for  the  purpose  of  separating  the 
lumps  of  the  resin,  and  thus  hastening  the  solution.  Stir  the  mixture 
occasionally. 

Add  the  mastic  to  the  chloroform  in  a  well-stoppered  bottle. 

When  the  solution  of  the  resins  is  complete  add  the  chloroform 
mixture  to  the  dammar,  and  keep  in  a  bottle  covered  with  a  plate  of 
glass.  After  the  dirt  from  the  gum  has  thoroughly  settled,  decant 
into  small  bottles  for  use.  Do  not  attempt  to  filter. 

I  have  histological  mounts  which  were  made  with  this  medium 
nearly  ten  years  since,  and  the  tissues  have  shown  no  deterioration 
whatever. 

DAMMAR   MOUNTING  VARNISH. 

No.  2. 

Bsst  dammar  varnish  of  the  paint-shops,  diluted  with  a  sufficient 
quantity  of  turpentine. 

I  do  not  know  that  this  is  in  any  way  inferior  to  the  last,  but  histol- 
ogists  generally  have  a  preference  for  media  of  known  composition. 
They  may  both  be  diluted  with  turpentine,  chloroform,  ether,  or  pure 
benzole;  or  thickened,  by  removing  the  stopper  of  the  bottle  until  a 
sufficient  amount  of  the  solvent  has  evaporated. 

XYLOL   BALSAM. 

Xylol  is  preferred  by  some  histologists  as  a  solvent  or  diluent  of 
Canada  balsam  for  general  mounting  purposes.  Xylol  dissolves  the 
balsam  very  readily  without  heat,  and  evaporates  more  rapidly  than 


198  PRACTICAL    MICROSCOPY. 

most  solvents.  A  thin  solution — say  xylol  two  parts  to  Canada  balsam 
one  part — should  be  first  prepared,  and,  after  filtering  through  paper, 
it  may  be  placed  in  an  unstoppered  bottle  until,  by  evaporation,  it  be- 
comes sufficiently  thick  for  use. 

Xylol  is  miscible  with  strong  alcohol,  oil  of  cloves,  etc.,  but  not 
with  water. 


VARNISHES    AND   CEMENTS    FOR  RINGING   MOUNTS. 

1.  Dammar. — I  believe  a  clean  dammar  mount,  with  circular  cover, 
neatly  labeled,  cannot  be  improved  in  appearance  by  painting  rings  of 
colored   varnish  around   the  specimen.     Nevertheless,  the  beginner 
will  purchase  and  use  a  turn-table,  and  must  be  therefore  directed  in 
its  employment. 

A  ring  of  dammar,  thinned  with  turpentine  so  as  to  flow  readily 
from  the  brush,  makes  a  very  neat  border  to  the  cover-glass  of  a 
specimen  mounted  in  this  medium.  Let  the  layer  be  quite  thin. 

2.  Zinc  Cement. — To  a  small  quantity  of  thin  dammar  varnish,  add 
q.  s.  of  pure  dry  zinc  white.     Mix  thoroughly  on  a  glass  plate  with 
paint-knife  or  spatula.     The  consistency  should  be  such  as  to  flow 
readily  from  the  brush. 

Before  adding  any  cement  containing  pigment  or  color  to  a  dammar 
mount,  a  protecting  covering  should  be  applied;  otherwise  the  cement 
will  eventually  creep  in  between  the  cover  and  the  slide  and  mix  with 
the  original  mounting  varnish.  It  may  proceed  very  slowly;  but  in 
time  the  specimen  will  be  surely  ruined.  This  is  best  avoided  by 
painting  a  thin  ring  around  the  edge  of  the  cover  of  liquid  glue. 
Cooper's  and  LePage's  are  both  excellent.  Let  this  dry,  and  any 
amount  of  varnish  may  be  subsequently  applied  without  disaster. 

Aniline  Colors.  Red,  blue,  etc.,  maybe  employed  by  dissolving  the 
dry  color  in  a  little  thin  shellac  varnish.  This  dries  quickly  and  may 
be  used  over  the  zinc. 

Oil  colors.  The  artists'  colors  which  are  sold  in  tubes  may  be  thinned 
with  dammar. 

Black  varnish.  This  is  the  ' '  Black  Japan  "  of  the  paint  shops.  It 
may  be  made  by  dissolving  gum  asphaltum  in  turpentine.  The  gen- 
uine asphaltum  is  very  difficult  to  procure,  as  coal  tar  is  generally  sold 
under  this  name.  It  is  therefore  best  to  purchase  the  'varnish,  thin- 
ning with  turpentine  or  pure  benzol  if  necessary. 

Shellac  Varnish. — The  best  orange  shellac  dissolved  in  strong 
alcohol,  in  quantity  sufficient  to  make  a  varnish  of  the  consistency 
of  treacle. 


FORMULAE.  199 

This  is  an  excellent  cement  for  glycerin  mounts.  It  should  be 
considerably  thinned  for  use  as  a  vehicle  for  color. 

PRESERVATIVE  FLUID. 

Acetate  of  Soda, 1  Ib. 

Distilled  Water, 8  ounces. 

Scraping  or  teasings  from  tissues,  morphological  elements  from 
urinary  sediment,  casts,  in  fact,  almost  any  histological  element  may 
be  indefinitely  preserved  in  this  solution.  It  is  important  that  the 
tissues,  etc.,  be  freed  from  organic  matters  in  solution,  before  being 
placed  in  the  preservative;  for  example:  urine  must  be  carefully 
decanted  from  the  sediment  to  be  preserved  before  the  acetate  solu- 
tion is  added.  I  am  enabled  to  preserve  the  different  forms  of  cells 
from  year  to  year,  for  my  classes,  in  small  bottles  of  this  fluid.  When 
a  demonstration  is  required,  it  is  simply  necessary  to  transfer  a  drop 
of  the  sediment,  by  means  of  a  pipette,  to  a  slide,  and  apply  the 
cover-glass.  , 

If  it  be  desired  to  preserve  such  a  mount,  wipe  the  edges  of  the 
cover  with  a  bit  of  blotting  paper,  and  seal  with  a  ring  of  shellac 
or  asphalt um  varnish,  or  zinc  cement,  applied  with  a  small  brush. 

NORMAL  SALT  SOLUTION. 

Chloride  of  Sodium  (common  salt),         .         *     7  grains. 
Distilled  Water, 2  fluidounces. 

A  medium  for  the  temporary  examination  of  fresh  tissues — scrap- 
ings, teasings,  etc. 

RAZOR-STROP  PASTE. 

Sulphate  of  iron  and  common  salt  equal  parts.  Calcine  in  a  sand 
crucible  at  a  dull  red  heat  for  ten  minutes.  When  cold,  grind  lightly 
in  a  porcelain  mortar  and  pass  through  fine  gauze.  Preserve  dry  in  a 
well-corked  bottle. 

A  few  grains  dusted  on  the  surface  and  mixed  with  a  minute  quan- 
tity of  tallow  will  add  greatly  to  the  efficiency  of  the  strop. 

Another. — Equal  parts  of  opticians'  rouge  and  the  finest  washed 
flour  of  emery,  mixed  with  a  sufficient  quantity  of  vaseline  to  make  a 
stiff  paste. 


200  PRACTICAL    MICROSCOPY. 

SILVER  STAINING  SOLUTION. 

Nitrate  of  Silver, 5  grains. 

Water  (distilled), 4  ounces. 

Used  for  the  demonstration  of  cement  substance  between  cell  elements. 

OSMIC  ACID  SOLUTION. 

Osmic  Acid, 1  gramme. 

Water, 100  cubic  cent. 

The  acid  is  found  in  market  sealed  in  glass  tubes  holding  one 
gramme  each.  The  utmost  care  should  be  taken  to  avoid  inhaling 
the  vapor  from  the  pure  acid  as  it  produces  an  intense  inflammation 
of  the  respiratory  surfaces.  The  best  method  of  handling  the 
material  is  to  measure  100  c.c.  of  water,  place  it  in  a  strong  bottle, 
and  then  drop  in  the  tube  containing  the  osmic  acid.  Then  with  a 
glass  rod  break  the  tube.  The  bits  of  glass  need  not  be  removed. 
Keep  the  bottle,  tightly  stoppered,  in  a  cool  dark  place. 

Osmic  acid  is  used  in  histology  on  account  of  its  action  upon  fatty 
substances,  i.  e.,  staining  them  of  a  deep  brown  or  black. 

WEIGERT'S     H^EMATOXYLIN     STAINING     FOR    MEDUL- 
LATED  NERVE  TISSUE. 

Formula. 

1.  A  saturated  aqueous  solution  of  neutral  acetate  of  copper. 

2.  Strong  haematoxylin  staining  fluid,  vide  text. 

3.  Borax,  ferridcyanide  of  potassium,  aa  1  drachm. 
Water 4  fluidounces. 

Process. 

1.  Allow  the  sections  to  remain  in  1  for  twenty-four  hours.* 

2.  Wash  in  clean  water  for  a  few  moments  only,  and  transfer  to  2. 
Brain  sections  will  require  from  two  to  three  days,  and  spinal  cord 
twenty-four  hours  for  complete  staining.     They  must  appear  almost 
black.     If  the  hardening  has  been  effected  with  the  bichromate  solu- 
tion as  given  in  the  text  (vide  hardening  fluids),   maceration  of  the 
sections  in  the  cupric  acetate  may  be  omitted. 

3.  Wash  in  water  for  five  minutes  and  transfer  to  3.     They  may  be 

*  The  haema.  solution  gives  the  best  results,  in  this  staining,  if  kept  at  tem- 
perature of  about  100°  F. 


KAKYOKINESIS.  201 

allowed  to  remain  for  twelve  hours  without  harm.     Generally  an  hour 
will  be  sufficient. 

4.  Wash  in  water. 

5.  Dehydrate  gradually,   first  placing  in  dilute  alcohol,  and  after- 
ward in  stronger.  The  sections  can  now  be  kept  in  alcohol  indefinitely* 
If  the  tissue  has  been  infiltrated  with  celloidin,  the  sections  must 
not  be  held  in  ninety-five  per  cent  alcohol  longer  than  five  minutes, 
as  the  infiltrating  medium  will  be  dissolved. 

6.  Clarify  with  oil  of  cloves — oil  of  bergamot  for  celloidin  speci- 
mens— and  mount  in  dammar. 

The  method  does  not  produce  bright  colors,  but  it  gives  a  very 
remarkable  differentation  of  nerve  tissue,  by  staining  the  medullary 
substance  violet,  and  the  axis  cylinders  brown.  It  is  particularly 
valuable  in  pathological  histology. 

BAYBERRY  WAX  INFILTRATING  METHOD. 

In  answer  to  many  inquiries  regarding  the  material  used  in  this 
process,  I  may  say  that  Messrs.  Eimer  &  Amend,  chemists,  of  New 
York,  from  whom  my  supply  was  originally  obtained,  state  that  the 
article  furnished  me  was  the  Japan  wax.  Dr.  J.  W.  Blackburn,  of 
Washington,  D.  C.,  kindly  informs  me  that  this  is  the  product  of 
Rhus  succedanea.  The  material  with  which  I  have  had  the  best  re- 
sults w<is  of  a  very  pale  yellow  or  canary  color.  The  darker  speci- 
mens are  unsuitable. 

KARYOKINESIS. 

The  phenomena  attending  cell-division  are  best  shown  in  the  thin 
gill-plates  or  caudal  fin  of  larvaB  of  the  salamandra.  Very  fair 
demonstrations  may  be  made  from  rapidly  growing  tumors,  as  carcino- 
matft,  if  after  removal  they  are  sliced  thin  and  immediately  fixed. 

Flemming's  Fixing  Fluid.* 

Chromic  acid,  0.25  per  cent  \ 

Osmicacid,  0.1       "          V  in  water. 

Glacial  acetic  acid,    0.1       "          ) 

Half-an-hour's  immersion  will  usually  suffice,  after  which  the  tissue 
is  rinsed  quickly  in  water  and  transferred  to  absolute  alcohol,  where  it 
may  remain  until  ready  to  cut.  The  parts  of  larvae,  above  mentioned, 
are  of  course  sufficiently  thin  without  sectioning. 

For  staining,  haema.  or  picro-carmine  answer  well,  although  saf- 
*  "  Microtomist's  Vade-mecum,"  Lee.  London,  1885. 


202  PRACTICAL    MICROSCOPY. 

franin  is  preferred  by  Strassburger.     A  saturated  solution  of  the  dye 
in  absolute  alcohol  is  diluted  with  an  equal  volume  of  water  and  al- 
lowed to  act  on  the  tissue  for  twenty-four  hours.     Wash  thoroughly 
with  absolute  alcohol,  clear  in  oil  of  cloves,  and  mount  in  dammar. 
The  highest  powers  are  necessary  for  successful  demonstration. 

FIXING    AND    STAINING  THE   CORPUSCULAR    ELE- 
MENTS  OF  BLOOD. 

The  following  method,  which  has  been  elaborated  by  Prof.  Gaule, 
of  Zurich,  will  prove  more  satisfactory  than  processes  which  involve 
the  drying  of  the  blood.  The  essential  steps  are: 

1.  Transferrence  to  the  slide.     This   must   be  accomplished  very 
quickly  to  provide  against  changes  in  the  corpuscular  elements  which 
occur  soon  after  removal  from  the  vessels.     If  to  be  taken  from  the 
living  animal — and  the  frog  is  best  for  beginners — the  surface  must  be 
scrupulously  clean,  a  small  vessel  punctured  with  the  needle,  and  a. 
minute  drop  of  blood  carried  to  the  surface  of  a  slide  by  means  of  a 
glass  rod.     The  blood  is  spread  in  a  thin  layer,  after  which,  and  be- 
fore drying,  the  elements  are  to  be  fixed. 

2.  Fixing. — A  portion,  say  fi.  §  ij.,  of  a  saturated  aqueous  solution 
of  bichloride  of  mercury  having  been  prepared  in  a  saucer,  the  blood 
slide  is  submerged  in  the  liquid.     Five  minutes  suffice  for  this  work. 

3.  Washing  is  accomplished  by  immersing  the  slide  for  a  moment 
in  a  saucer  of  distilled  water,  after  which  the  action  is  completed  by 
placing  in  absolute  alcohol  for  five  minutes.     Drain  on   bibulous 
paper  for  a  moment. 

4.  Staining. — Moisten  the  blood  with  a  little  distilled  water,  drain, 
and  afterward  drop  a  few  minims  of  haema.  solution  on  the  horizon- 
tally placed  slide.     Ordinary  haema.  will  answer  perfectly  if,  to  about 
a  drachm  of  the  solution,  two  drops  of  alcohol  are  added.     The  stain- 
ing is  complete  in  five,  minutes.     Wash  in  distilled  water,  and  again 
stain  as  before  with   a   one-per-cent  aqueous  solution  of  nigrosin. 
Again  wash  with  distilled  water,  and  again  stain  as  before  with  eosin 
one  part,  alcohol  50  parts,  distilled  water  150  parts,  for  one  minute. 

5.  Mounting. — A  permanent   specimen  is   completed  by  washing 
the  film  of  blood  with  strong  alcohol.     A  drop  of  oil  of  cloves  gives 
transcluceucy  in  a  moment,  after  which  it  is  drained  off,  a  drop  of 
dammar  added,  and  the  cover  applied. 

The  nuclei  of  the  red  corpuscle  of  the  frog  take  the  blue  haema. f 
while  a  variety  of  white  corpuscle  with  a  large  round  or  spindle-shaped 
nucleus — the  hcematoblast  of  Hayem — has  its  protoplasm  stained 


FIXING    BLOOD-CORPUSCLES.  203 

blue-black  by  the  nigrosin.  Ehrlich  has  given  the  name  eosinophilous 
cells  to  those  white  corpuscles  with  several  nuclei  whose  granular  pro- 
toplasm takes  the  eosin  deeply.  Other  forms  of  colorless  blood-cor- 
puscles as  amcebocytes  and  endothelioid  cells  are  differentiated  by  this 
mode  of  fixing  and  triple  staining.  The  highest  powers  of  the  micro- 
scope are  required. 


INDEX. 


Abbe  condenser,  4 
Abdominal  cavity,  162 

salivary  gland,  159 
Aberration,  chromatic,  2 
spherical,  2 

Absorption  from  intestine,  88 
Acetate  of  copper,  200 
Acid,  acetic,  31 

chromic,  22 
hydrochloric,  22 
nitric,  22 
osmic,  49 

osmic,  solution,  200 
picric,  26 
Acini,  compound, 155 

simple,  155 
Acinous  glands,  155 
Adenoid  reticulum,  167 
tissue,  61,  167 
tissue  in  thymus  body,  178 
tissue,  Klein  on,  167 
Adipose  tissue  in  bronchi,  99 
Adventitia  of  arteries,  66 
Afferent  glomerular  arterioles,  125 
Agents,  staining,  25 
Agminate  glands,  91 
Ailantus  pith,  13 
Air,  atmospheric,  100 
bubbles,  36 
sacs,  100 
vesicles,  100 

Albuminate  of  silver,  164 
Albuminous  cement,  163 
Alcohol  "  A,"  "  B,"  and  "  C,"  21 

hardening,  20 
Alum,  25 
Alveoli,  gland,  155 

pulmonary,  100 
Amoebocytes,  203 
Ampulliform  dilatation,  97 
Aniline  colors,  198 
Anterior  commissure,  185 

median  fissure,  185 
Appendages  of  skin,  71 
Appendix,  xiphoid,  58 
Arachnoid,  191 


Arcade,  arterial,  124 

Areas,  physiological,  of  spinal  cord, 

185 

Areolar  tissue,  51 
Arrectores  pili,  74 
Arrowroot  starch,  38 
Arterial  arcade,  124 
Arteries,  66 

adventitia  of,  66 
intima  of,  66 
large,  67 

lymphatics  of,  162 
media  of,  66 
Arteriolae  rectae,  126 
Artery,  bronchial,  95,  98 

hepatic,  107 

phrenic,  150 

pulmonary,  99 

renal,  124,  150 

splenic,  173 

typical,  66 

Articular  cartilage,  56 
Artificial  gastric  fluid,  22 
Ascending  limb  of  Henle,  123 
Asphaltum,  198 
Atmosphere,  100 
Attachment,  freezing,  16 
Auerbach's  plexus,  86,  91 
Author's  microtome,  15 
Axis  cylinder,  180 

Bacteria  in  urine,  37 
Balsam,  xylol,  197 
Basement  membrane,  99 

membrane  of  corium,  71 
Bayberry  tallow,  22,  201 
Beaker  cells,  97 
Bellini,  tubule  of,  124 
Bergamot  oil,  27 
Bichromate  of  potash,  22 
Bile  capillaries,  108 

ducts,  origin  of,  118 
Bipolar  cells,  50 

nerve  cells,  181 
Birds,  blood  of,  48 
Blackburn,  Dr.  J.W.,  201 


306 


INDEX. 


Black  japan,  198 

varnish,  198 
Bladder  of  frog,  62 

urinary,  149 
Blood  corpuscle  as  test,  7 

corpuscle,  colorless,  49 

corpuscle,  red,  47 

corpuscles,  staining,  203 

corpuscles,  white,  49 

fixing  and  staining,  202 

of  birds,  48 

of  camelidae,  48 

of  fishes,  48 

of  invertebrates,  48 

of  reptiles,  48 

oxygenation  of,  100 

plates,  48 

supply,  hepatic,  106 

supply  of  ovary,  149 

supply  of  spleen,  173 

vessels,  66 

vessels  of  bronchi,  98 

vessels  of  epineurium,  182 

vessels  of  glands,  150 

vessels  of  kidney,  124 

vessels  of  omentum,  67 

vessels  of  pulmonary  alveolus, 
67 

vessels  of  skin,  70 

vessels  of  spinal  cord,  189 

vessels,  pulmonary,  99 
Bodies,  Malpighian,  of  kidney,  122 

Malpighian,  of  spleen,  173 
Body,  suprarenal,  120,  150 

thymus,  177 
Bone,  58 

corpuscles,  59 

decalcifying,  22 

mounting  of,  61 
Borax  carmine  staining  fluid,  26 

carmine  staining  process,  30 
Bowman,  capsule  of,  122 
Bowman's  muscle  discs,  65 
Brain,  191 

ganglia  of,  191 

gray  matter  of,  191 

hardening  of,  192,  200 

lymph  cavities  of,  191 

membranes  of,  191 

neuroglia  of,  182 

section  cutting  of,  192 

sulci  of,  191 

white  matter  of,  191 
Branched  tubular  glands,  154 
Bronchial  artery,  98 

glands,  96,  154 
tube,  94 
vein,  98 
Bronchi,  94 

adipose  tissue  in,  99 
basement  membrane  of,  99 
blood-vessels  of,  98 


Bronchi,  cartilage  in,  98 

glands  of,  98 

mucosa  of,  98 

muscular  coat  of,  98 

nerves  of,  98 

staining  of,  97 

subdivision  of,  94 

terminal,  97,  101 
Bronchus,  layers  of,  95 

of  pig,  44 
Brood  nests,  179 
Brownian  movement,  36 
Brunner's  glands,  89 
Bubbles,  air,  36 
Buccal  epithelium,  41 

Cable,  telegraphic,  181 
Calyces  of  kidney,  120 
Camelidae,  48 
Canal,  central,  186 
Canaliculi,  58 
Canal,  portal,  108 
Canals,  dentinal,  78,  81 

Haversian,  59 
Cancer,  epithelial,  179 
Capillaries,  66 

bile,  108 
lymphatic,  161 
of  glands,  153 
of  ovary,  149 
of  supra- renal  body,  150 
stomata  of,  67 
tortuous,  in  lung,  103 
Capsule  of  Bowman,  122 
of  Glisson,  106 
of  kidney,  120 
of  lymph  nodes,  167 
of  thymus  body,  177 
supra-renal,  150 
Carcinomata,  201 
Cardiac  gland-tubes,  84 

muscular  fibre,  65 
Care  of  objectives,  34 

of  the  microscope,  34 
Carmine  and  picric  acid  staining,  31 
movement  of  particles  of,  36 
No.  40,  26 
staining  fluid,  26 
Carpenter,  Prof.  Wesley  M.,  11 
Cartilage,  56 

articular,  56 
corpuscles,  56 
elastic,  57 
fibro-,  56 
hyaline,  56 
plates  in  bronchi,  98 
reticular,  57 

Casts,  urinary,  preserving,  199 
Caudal  fin,  201 
Cavities,  lymphatic,  161 
Cavity,  abdominal,  162 
cranial,  191 


INDEX. 


207 


€avity,  spinal,  191 

thoracic,  162 
Cell  body,  39 
cement,  163 
distribution,  40 
division,  201 
primordial,  147 
proliferation,  40,  201 
structure,  Ehrlich  on,  203 
typical,  146 
wall,  39 

-Celloidin  intiltration,  23 
Cells,  beaker,  97 

bipolar,  50 

bipolar  nerve,  181 

border,  85 

central,  85 

chief,  85 

ciliated,  45 

ciliated  from  oyster,  45 

columnar,  44 

covering,  51 

Deiter's,  183 

endothelial,  51 

endothelioid,  203 

eosinophilous,  203 

epithelial,  51 

flat,  41 

ganglion,  181 

glandular,  51 

goblet,  97 

hepatic,  109 

in  urine,  143 

lining,  51 

lymphoid,  61,  161 

mucous,  97 

multinucleated      in       thymus 
body,  179 

multipolar,  50 

rnultipolar  nerve,  181 

nerve,  50,  181 

of  Purkinje,  194 

outlining  of,  by  silver  nitrate, 
164 

parietal,  85 

polar,  47,  50 

polyhedral,  49 

quadripolar  nerve,  181 

spheroidal,  47 

spider,  183 

stellate,  47,  50 

tailed,  from  pelvis  of  kidney, 

140 
teased,  hepatic,  113 

tripolar,  50 

tripolar  nerve,  181 

typical,  39 

unipolar,  50 

unipolar  nerve,  181 

uterine,  136 

vacuolated,  of  bladder,  143 

vaginal,  136 


Cells,  variation  in  form,  40 
Cement,  cell,  163 
zinc,  198 

Central  canal,  186 
Cerebellar  tracts,  direct,  185 
Cerebellum,  194 

cortex  of,  194 
folia  of,  194 
Cerebral  layers,  192 
Cerebro-spinal  system,  180 
Cerebrum,     practical    demonstration 

of,  192 

staining  of,  192 
Cervix  uteri,  glands  of,  154 
Chains,  Graanan,  147 
Chamois  leather,  34 
Change,  retrograde,  20 
Channels,  lymph,  161 
spleen,  173 

Chinks,  lymphatic,  161 
Chloroform,  Squibb's,  197 
Chromatic  aberration,  2 
Chromic  acid  hardening,  21 

acid  fixing,  21 
Chyle  receptacle,  161 
Chylopoietic  viscera,  106 
Cicatricial  tissue,  146 
Ciliated  cells  from  oyster,  45 

columnar  cells,  45 
Circulation,  lymphatic,  161 
Cirrhptic  liver,  cells  from,  52 
Cleaning  cover  glasses,  31 

slides,  31 

Clefts,  lymphatic,  161 
Clove  oil,  28 

oil,  removal  of,  33 
Coarse  adjustment,  1 
Coiled  tubular  glands,  154 
Collecting  tubule,  124 
Collodion,  24 
Color  in  air  bubbles,  36 
Coloring  drawings,  9 
Colorless  blood-corpuscles,  49 
Colors,  aniline,  198 

oil,  198 

Column  of  Goll,  187 
Columnar  cells,  44 
Columns,  postero-external,  185 
cortical,  120 
postero-internal,  185 
Commissure,  anterior  gray,  185 
posterior  gray,  186 
white,  185 
Compound  acini,  155 

acinous  gland,  157 
Concavity  of  blood  discs,  48 
Condenser,  4 

Abbe,  4 

Conducting  portion  of  nerves,  180 
Conductor,  electrical,  181 
Coniferous  wood,  38 
Connective-tissue  corpuscles,  51 


208 


INDEX. 


Connective  tissue  of  liver,  106 
tissue  of  lung,  99 
tissue  of  nervous  system, 

182 

tissue  of  pancreas,  159 
tissue  of  parotid  gland,  157 
tissues,  51 
tissues,  special,  61 

Conservation  of  vision,  7 

Constrictions  of  Ranvier,  181 

Contractile  rods,  63 

Convoluted  tubule,  122 

Cooper's  glue,  198 

Copper,  acetate,  200 

sulphate  of,  22 

Cords,  follicular,  167 

Cord,  spinal,  185 

Corium,  69 

basement  membrane  of,  71 

Cork  support,  19 . 

Corn  starch,  38 

Cornu  of  spinal  cord,  185 

Corpuscles,  blood,  203 

blood,  fixing  of,  202 
bone,  59 
cartilage,  56 
connective-tissue,  51 
Hassal's,  179 
lymph,  174 
pus,  49 

salivary,  37,  41 
tactile,  71 

Corpus  luteum ,  144,  146 

Cortex  of  cerebellum,  194 
of  kidney,  120 
of  thymus  body,  178 

Cortical  columns,  120 

Corundum  hones,  17 

Cotton  fibres,  37 

Cover  glass,  31 

glass,  pressure  of,  36 

Covering  cells,  51 

Crossed  pyramidal  tracts,  185 

Crusta  petrosa,  80,  81 

petrosa,  lacunae  of,  80 

Crypts  of  Lieberkiihn,  89 

Crystals,  fat,  55 

Cul-de-sac,  vaginal,  136 

Currents,  thermal,  36 

Cuticula,  78 

Cylinder,  axis,  180 

Dammar,  mode  of  using,  33 
varnish,  i$4   :  -»  *• 
Decalcification,  61 

of  teeth,  22,  80 
Decalcifying  of  bone,  22 
Degeneration,  fatty,  155 
Dehydrating  tissues,  28 
Deiter's  cells,  183 
Dentinal  canals,  78,  82 
elements,  82 


Dentinal  fibres,  78,  82 
sheath,  82 
striae,  82 
Dentine,  78,  81 
Deposits,  urinary,  135,  143 
Derma,  69 

basement  membrane  of,  71 
Descending  limb  of  Henle,  123 
Development  of  ovum,  147 
Diameter  of  kidney  tubes,  122,  123 
Diaphragm,  central  tendon  of,  163 
Differentiation  of  cell  elements,  2U& 
Disc,  Hensen's,  63 
Discs,  intervertebral,  57 

of  Bowman,  65 
Discus  proligerus,  146 
Dissociating  fluids,  9 

process,  22 

Distal  convoluted  tubule,  123 
Distilled  water,  163 
Distribution,  cell,  40 
Direct  cerebellar  tracts,  185 
pyramidal  tracts,  185 
Division  of  cells,  201 
Dog,  kidney  of,  127 
stomach  of,  86 
Double  staining,  29,  31 
Drainage,  tissue,  161 
Duct,  hepatic,  106 
lymph.  90 
pancreatic,  159 
papillary,  124 
Ductless  glands,  173 
Ducts,  lymphatic,  161 
mesenteric,  162 
thoracic,  162 
Dura  mater,  191 
Dust  on  lenses,  34 

Efferent  glomerular  arteriole,  125 
veins  of  lymph  nodes,  167 
Ehrlich  on  cell  elements,  203 
Elastic  cartilage,  57 

lamina  of  blood-vessels,  66 
tissue,  52 

tissue  in  bronchi,  98 
Elder  pith,  13 
Electrical  conductor,  181 
Elements,  dentinal,  82 

of  ganglia,  181 
sarcous,  65 
structural,  35 
structural,  of  nervous  sys- 
tem, 180 

Embryonic  tissue,  62 
Emery,  flour  of,  199 
Enamel  of  teeth,  79 
prisms,  79 
Endomysium,   64 
Endoneurium,  182 
Endothelial  cells,  51 
Endothelioid  cells,  203 


INDEX. 


209 


Endothelium,  44 

of  blood-vessels,  66 
Eosin  solution,  26 
staining,  203 
Eosinophilous  cells,  203 
E.  P.  E.  N.  formula,  182 
Epidermis,  68 
Epineurium,  182 

lymph-spaces  of,  182 

vessels  of,  182 
Epithelia,  glandular,  50 
Epithelial  cancer,  179 

cells,  51 
Epithelium,  buccal,  41 

of  bladder,  142 

of  ovary,  148 

of  tongue,  41 

pavement,  42 

proliferation  of,  135 

stratified,  41 

squamous,  41 

tesselated,  42 

transitional,  41 

uterine,  136 

vaginal,  136 
Ether  freezing,  16 
Eustachian  tube,  58 
Extraneous  substances,  37 

substances,  mounting  of, 

38 

Eye-lens,  3 
Eye-piece,  1 

Fasciculi,  primitive,  64 
Fat  columns  of  Satterthwaite,  70 
crystals,  55 
globules  in  milk,  35 
globules  in  suprarenal  capsule,  152 
tissue,  54 

Fatty  degeneration,  155 
Fauces,  158 
Feathers,  38 

Fenestrated  membrane,  66 
Fermentation  spores,  38 
Ferrein,  pyramids  of,  122,  124 
Fibres,  cotton,  37 

dentinal,  78,  82 
linen,  37 
nerve,  180 
perforating,  59 
silk,  37 
wool,  37 
Fibroblasts,  51 
Fibro-cartilage,  56 
Fibrous  tissue,  51 
Field  lens,  3 

of  view,  5 
Fin,  caudal,  201 
Fine  adjustment,  1 
Fishes,  blood  of,  48 
Fissure,  anterior  median,  185 
posterior  median,  185 
14 


Fissure,  transverse,  of  liver,  106 
Fixing  blood  elements,  202 

chromic  acid,  21 

fluid,  Flemming's,  201 
Flat  cells,  41 
Flour  of  emery,  199 
Fluid,  artificial  gastric,  22 

dissociating,  9 

Flemming's  fixing,  201 

lymphatic,  161 

preservative,  199 
Focal  adjustment,  5 
Focussing,  1,  5 
Fcetal  life,  147 

lung,  103 

ovary,  148 

teeth,  80 
Folia  of  cerebellum,  194 

of  suprarenal  bodies,  150 
Follicle  of  hair,  71 
Follicles  of  Lieberktihn,  91 
solitary,  90 
of  thymus  body,  177 
Follicular  cords,  167 
Foramen  dentium,  78 
Form  of  objects,  35 
Formulae,  miscellaneous,  197 
Fourth  ventricle,  186 
Freezing  attachment,  16 
Fresh  tissue,  20 
Frog,  bladder  of,  62 
Frog's  mesentery,  42 
Funiculus  cuneatusof  spinal  cord,  187 
gracilis  of  spinal  cord,  137 

Gage,  Professor,  on  Japanese  paper,  31 
Gall  duct,  107 
Ganglia,  nerve,  181 

of  brain,  191 
Ganglion  cells,  181 

cells,  poles  of,  181 
elements  of  a,  181 
Gastric  fluid,  artificial,  22 
juice,  83 
tubules,  83 
Gaule,  Professor,  202 
Gelatinous  substance,  185 
Genito-urinary  tract,  135 
Germinal  spot,  146 

vesicle,  146 
Gill  plates,  201 
Gland  alveoli,  155 

mammary,  155 
parotid,  156 
sebaceous,  73 
serous,  159 
sublingual,  157 
submaxillary,  158,  160 
sudoriferous,  71 
thymus,  177 
Glands,  153 

acinous,  155 


210 


INDEX, 


Glands,  agminate,  91 

branched  tubular,  154 

bronchial,  96,  154 

Brunner's.  89 

buccal,  157 

coiled  tubular,  154 

ductless,  173 

essentials  of,  153 

gastric,  154 

intestinal,  154 

mucous,  158 

mucous  of  bronchi,  98 

of  cervix  uteri,  154 

parenchyma  of,  153 

peptic,  83 

Peyer's,  154 

pvloric,  84 

salivary,  153,  157 

sebaceous,  155 

sudoriferous,  154 

uterine,  154 

vessels  of,  153 
Glandular  cells,  50 

epithelia,  50 

structures,  staining  of,  159 
Glassy  membrane  of  hair,  71 
Glisson's  capsule,  106 
Globules,  oil,  36 
Glomerulus  of  kidney,  125 
Glue,  Cooper's,  198 

Le  Page's,  198 
Glycerin  in  honing,  17 

in  mounting,  128 
Goll,  column  of,  187 
Goose  flesh,  74 
Graafian  chains,  147 
follicles,  144 
Granules,  pigment,  152 
Gray  commissure,  185 

matter  of  brain,  191 
nerve  matter,  181 
Gum,  dammar,  197 
mastic  197 

Hsematoblast,  202 
Hsematoxylin,  25 

and  eosin,  29 
staining  fluid,  25 
staining  process,  27 
Weigert's,  200 
Hair,  37,  71 

cortex  of,  91 
follicle,  71 

follicle,  muscle  of,  74 
glassy  membrane  of,  71 
from  shaving,  74 
medullated,  71 
permanent  mounting  of,  74 
root-sheath  of,  71 
transverse  section  of,  71 
Hardening,  alcohol,  20 

bayberry  tallow,  22 


Hardening  by  freezing,  24 

chromic  acid,  21 

of  bladder,  135 

of  brain,  192 

of  fcetal  ovary,  147 

of  genito-urinary  organs, 
135 

of  kidney,  127 

of  liver,  110,113 

of  tissues,  20 

of  nerve  fibre,  180 

of  os  uteri,  135 

of  ovary,  144 

of  pancreas,  159 

of  parotid  gland,  159 

of  small  intestine,  92 

of  spinal  cord,  186 

of  spleen,  174 

of  submaxillary  gland,159 

of  suprarenal  capsule,  150 

of  thymus  body,  177 

of  ureters,  135 

of  uterus,  135 

quick,  21 

with  Miiller's  fluid,  22 
Hartnack  objectives,  4 
Hassal's  corpuscles,  179 
Haversian  canals,  59 

system,  59 

Hayem's  hsematoblast,  202 
Heitzmann,  Dr.  Carl,  61 

on  development  of  teeth, 

80 
Henle,  loop  of,  123 

tubule  of,  123 
Hensen's  middle  disc,  63 
Hepatic  artery,  107 

blood-supply,  106 
cells,  109 
cells,  teased,  113 
duct,  106 
lobules,  106 
veins,  106 

Hilum  of  kidney,  120 
Hone,  17 

water  of  Ayr,  17 
Horns  of  ganglion  cells,  181 
Horny  layer  of  skin,  68 
Hyaline  cartilage,  55 
Hydrocarbons,  88 
Hydrochloric  acid,  22 

Ileum,  section  of,  92 

Illumination,  4 

Imbedding  with  ailantus  pith,  13 

with  paraffin,  13 
Incremental  lines,  79 
Infiltrating  with  bayberry  tallow,  22 
Infiltration  with  celloidin,  23 
Infundibula  of  kidney,  120 

pulmonary,  101 
Injection  of  lung,  101 


INDEX. 


211 


Insects,  38 

Intima  of  arteries,  66 
Interglobular  spaces,  78,  82 
Interlobular  septa  of  lung,  100 
veins,  106 

vessels  of  kidney,  124 
Internal  elastic  lamina,  66 
Intervertebral  discs,  57 
Intestinal  lymphatics,  90 

villi,  88 
Intestine,  coats  of,  88 

of  rabbit,  45,  92 

sinal1,  88 

Invertebrates,  blood  of,  48 
Involuntary  muscle,  63 

Japan,  black,  198 

wax,  201 

Japanese  paper,  31,  34 
Juice,  gastric,  83 

Karyokinesis,  201 

Kidney,  120 

afferent  vessels  of,  129 
arterial  arcade  of,  129 
blood-vessels  of,  124 
boundary  region  of,  144 
Bowman's  capsule  of,  129 
calyces  of,  120 
capsule  of,  120,  129 
collecting  tubes  of,  132 
convoluted  tubes  of,  129 
cortex  of,  120 
cortical  labyrinths  of,  129 
diagram  of,  121 
efferent  vessels  of,  129 
Ferrein's  pyramids  of,  129 
glomerulus  of,  130 
hardening  of,  127 
Henle's  limb,  130 
Henle's  loop  of,  130 
hilum  of,  120 
infundibula  of,  120 
interlobular  blood-vessels  of, 

129 
intertubular    capillaries  of, 

144 

labyrinths  of,  129 
lymphatics  of,  120 
Malpighian  bodies  of,  129 
Malpighian  pyramids,  129 
markings,  129 
medullary  portion  of,  133 
medullary  radii  of,  129 
papillary  ducts  of,  134 
pelvis  of,  120,  140 
principal  tubes  of,  134 
scheme  of,  121 
spiral  tubes  of, 
tubes,  122 

tubules,  diagram  of,  123 
tubules  of,  154 


Klein  on  adenoid  tissue,  167 

on  neuroglia,  195 
Knives,  sharpening,  16 
Krause's  line,  63 

Labels  for  slides,  34 
Laboratory  microscope,  2 
microtome,  15 
Labyrinth,  kidney,  122 
Lacteals,  90 
Lacunae,  58 

of  crusta  petrosa,  80 
Lamellae,  bone,  59 
Lamina,  internal  elastic,  66 
Laminae  of  crusta  petrosa,  80 
Larvae  of  salamander,  201 
Lateral  tracts,  185 
Layers  of  cerebrum,  192 
of  epidermis,  68 
Lenses,  cleaning  soiled,  34 

water,  36 

Le  Page's  glue,  198 
Leucocythaemia,  spleen  in,  176 
Lieberkutm,  crypts  of,  89 
Life,  foetal,  147 
Lifting  sections,  27 
Ligamentum  nuchas,  53 
Light,  transmitted,  10 
Limb  of  Henle,  123 
Limiting  membrane,  39 
Line,  Krause's,  63 

Purkinje's,  82 
Linen  fibres,  37 

for  optical  surfaces,  34 
Lines,  incremental,  79 

of  Retzius,  80 
Lining  cells,  51 

of  stomach,  83 
Links,  Graafian,  147 
Liquor  potassae,  26 
Liver,  105 

connective  tissue  of,  106 

lobules  of,  106 

of  pig,  116 

parenchyma,  108,  116 

physiological  scheme,  109 

practical  demonstration,  109 

scheme  of  structure,  106 
Lobes  of  thy m us  body,  177 
Lobular  parenchyma  of  liver,  108 
Lobule,  primary,  100 
Lobules,  hepatic,  106 

of  thymus  body,  177 
Loop  of  Henle,  123 
Lung,  94 

connective-tissue  of,  99 

foetal,  103 

hardening  of,  103 

injected,  102 

interlobular  septa,  100 

of  pig,  103 

parenchyma  of,  100 


212 


INDEX. 


Lung,  staining  of,  1 03 

vascular  supply  of,  100 
Lymph,  161 

cavities  of  brain,  191 
ducts  of  intestine,  90 
node,  diagram  of,  168 
node,    practical  demonstra- 
tion of,  169 
nodes,  91,  167 
nodes,  capsule  of,  167 
nodes,  sectioning,  169 
nodes,  staining,  169 
nodes,  trabeculse  of,  167 
nodes,   vascular  system  of, 

167 

paths,  164 

paths,  valves  of,  164 
spaces  in  portal  canals,  116 
spaces  of  nerves,  182 
spaces  of  perineurium,  182 
spaces  of  spinal  cord,  190 
spaces  of  thymus  body,  178 
Lymphatic  capillaries,  161 
ducts,  161 
system,  161 

Lymphatics  of  intestine,  90 
of  kidney,  120 
perivascular,  162,  190 
Lymphoid  cells,  61,  161 

Magnification  of  movements,  36 
Magnifying  power,  7 
Malpighian  bodies  of  spleen,  173 
Malpighii,  pyramids  of,  120 
Mammary  gland,  155 
Markings,  kidney,  129 
Mastic,  197 

Measurement  of  objects,  7 
Media  of  arteries,  66 
Medico-legal  work,  103 
Medulla,  186 

of  hair.  71 

of  thymus  body,  178 
Medullated  nerves,  180 
Meissner's  plexus,  91 
Membrana  granulosa,  146 

propria  of    kidney  tube, 

122 
Membrane,  basement,  99 

basement  of  corium,  71 

fenestrated,66 

glassy,  71 

limiting,  39 

peridental,  81 

tubular,  181 

Membranes  of  brain,  191 
Menopause,  144 
Merck's  hasmatoxylin,  25 
Mesenteric  ducts,  25 
Mesentery,  silvered,  42 
Method  in  observation,  6 
Weigert's,  186 


Micrometers,  8 
Microscope,  1 

adjustment,  4 
care  of,  34 
sketching  from,  8 
Microtome,  laboratory.  15 
Schrauer,  14 
Stirling,  12 
the  author's,  15 
Milk,  fat  globules  in,  35 
Mirrors,  4,  5 

Miscellaneous  formulae,  197 
Molecular  movement,  37 
Mordants,  30 

Morphology,  Dr.  C.  Heitzmann's,  80" 
Mounting  objects,  31 

extraneous  substances,  38 
varnish,  197 
Mounts,  rings  on,  34 
Movement,  Brownian,  36 
molecular,  37 
vital,  37 

Movements,  magnification  of,  36 
Mucosa  of  bronchi,  98 

of  pelvis  of  kidney,  140 
of  small  intestine,  88 
of  stomach,  83 
of  ureter,  141 
of  uterus,  136 
of  vagina,  136 
Mucous  glands,  158 

glands  of  bronchi,  98 
Miiller,  capsule  of,  122 
Miiller's  fluid,  22 

fluid,  hardening  with,  22 
Multinucleated  cells  of  thymus  body, 

179 

Multipolar  nerve  cells,  181 
Muscle,  62 

cardiac,  65 
from  tongue.  65 
non-striated,  62 
of  hair  follicle,  74 
striated,  63 

Muscular  coat  of  bronchi,  98 
Muscularis  mucosae  of  stomach,  83 

Nerve  cells,  50,  181 

cells,  bipolar,  etc.,  181 

functioning,  181 

ganglia,  181 

spinal,  185 

staining,  Weigert's,  200 

trunks,   connective   tissue  of, 

181 
Nerves,  conducting  portion  of,  180 

of  special  sense,  181 
Network,    intracellular,    in    hepatic 

cells.  117 
Neurilemma,  180 
Neuroglia,  61,  181,  186, 
Klein  on,  194 


INDEX. 


213 


Nigrosin,  203 

Nitrate  of  silver  solution,  26J 

Nodes,  lymph,  167 

of  Ranvier,  181 
Non-medullated  nerves,  181 
Non-striated  muscle,  62 
Normal  salt-solution,  180, 199 
Nuclei  of  cells,  39 
Nucleoli  of  cells,  39 

Objectives,  1, 
Objects,  form  of,  35 

movement  of,  36 
Odontoblasts,  78,  81 
Oil  colors,  198 
globules,  36 
of  bergamot,  27 
of  cloves,  28 
Omentum,  55 

vessels  from,  67 
Optical  axis,  5 
Optician's  rouge,  199 
Organisms  in  urine,  37 
Organs,  urinary,  135 
Origin  of  bile  ducts,  118 
Osmic  acid,  49 

acid  solution,  200 
Osier,  Prof. ,  48 
Os  uteri,  136 
Ova,  146 
Ovary,  144 

blood  supply  of,  149 
corpus  luteum  of,  144 
Graafian  follicles  of,  144 
practical  demonstration,  144 
Ovum,  development  of,  147 
Ox,  spinal  cord  of,  186 
Oxygenation  of  blood,  100 
Oyster,  ciliated  cells  from,  45 

Pancreas,  153, 

practical  demonstration  of, 

159 

Paper,  Japanese,  Prof.  Gage  on,  34 
Papillary  ducts,  124 

eminence,  120 
Paraffin  cement,  11 

imbedding,  13 
soldering,  18 
Parenchyma,  51 

of  glands,  153 
of  liver,  108,  116 
of  lung,  100 
Parotid  gland,  156 

gland,  parenchyma  of,  159 
practical    demonstration    of, 

159 

Paste,  razor-strop,  199 
Patch,  Peyer's,  91 
Pavement  epithelium,  42 
Pelvis  of  kidney,  140 
Pepsin,  22 


Peptic  glands,  83 

Perforating  fibres  of  Sharpey,  59 

Perichondrium,  96 

Peridental  membrane,  81 

Perimysium,  64 

Perineurium,  lymph  spaces  of,  182 

Periosteum,  59 

Peripheral  nerve  termini,  183 

Peritoneum,  163 

of  stomach  and  intestines, 

83 
Perivascular  lymphatics,  162,  190 

lymph-spaces     of     cere- 
brum, 193 
Peyer's  patch,  91 
Phrenic  artery,  150 
Pia  mater,  191 
Picric  acid  solution,  26 
Pig,  bronchus  of,  45 
kidney  of,  127 
liver  of,  116 
spinal  cord  of,  186 
Pig's  lung,  113 

Pigment  in  suprarenal  capsule,  152 
Plates,  blood,  48 

cartilage,  98 
Pleura,  100,  162 
Plexus,  Auerbach's,  86,  91 

Meissner's,  91 

Pencilling  of  serous  surfaces,  162 
Polar  cells,  47,  50 
Poles  of  ganglion  cells,  181 
Pollen,  39 
Polyhedral  cells,  49 
Portal  canal,  108 

vein,  106 

Posterior  commissure,  185 
Postero-external  columns,  185 
Posterp-internal  columns,  185 
Potassium  ferrid cyanide,  200 
Potato  starch,  38 
Power,  magnifying,  7 
Practical  demonstration.     Bronchus 

of  pig,  97 

demonstration.     Cerebel- 
lum, 196 
demonstration.    Cerebrum, 

192 
demonstration.     D  e  v  e  lop- 

ment  of  ovary,  147 
demonstration.      Human 

liver,  113 
demonstration.      Human 

lung,  105 
demonstration.     Intestine, 

92 

demonstration.  Kidney,  140 
demonstration.     Liver  of 

pig,  109 

demonstration.  L  y  m  pha- 
tics  of  central  tendon 
of  diaphragm,  163 


214 


INDEX. 


Practical  demonstration.    Mesenteric 

lymph  node,  169 
demonstration.    Ovary,  144 
demonstration.     Pancreas, 

159 
demonstration.     Parotid 

gland,  159 
demonstration.  Spinal  cord, 

186 

demonstration.  Spleen,  173 
demonstration.  Stomach,  87 
demonstration.  Submaxil- 

lary  gland,  159 
demonstration.    S  u  p  r  are- 

nal  capsule,  150 
demonstration.     Teeth,  81 
demonstration.    T  h  y  m  u  s 

body,  177 
demonstration.     Urinary 

bladder,  141 

demonstration.  Ureter,  140 
demonstration.  Uterus,  138 
demonstration.  Vagina,  138 
Preservative  fluid,  199 
Pressure  of  cover,  36 
Prickle  cells  of  skin,  69 
Primitive  fasciculi,  64 
Primordial  cell,  147 
Prismatic  color  in  air  bubbles,  36 
Prisms,  enamel,  79 
Process,  decalcifying,  22 
dissociating,  22 
Processes  of  odontoblasts,  82 
Proliferation,  cell,  40,  201 
Protoplasm,  89 

Proximal  convoluted  tubule,  122 
Pulmonary  alveoli,  100 
artery,  99 
infundibula,  101 
Pulp  of  teeth,  78 
spleen,  173 
Purkinje,  cells  of,  194 

granular  layer  of,  79 
Purkinje's  line,  82 
Pus  corpuscles,  49 
Pyloric  glands,  84 
Pyramidal  tracts,  185 
Pyramids  of  Ferrein,  122 

of  Malpighii,  120 

Quadripolar  nerve  cells,  181 
Quick  hardening,  20 

Rabbit,   central  diaphragmatic    ten- 
don of,  163 
intestine,  45,  92 
kidney  of,  127 
spinal  cord  of,  187 
Ranvier's  nodes,  181 
Rapid  hardening,  21 
Razor  stropping,  18 

strop  paste,  199 


Receptaculum  chyli,  91,  161 
Red  blood-corpuscle,  47 

muscle,  63 

Renal  artery,  124,  150 
Reptiles,  blood  of,  48 
Reservoir,  lymph,  161 
Rete  Malpighii  of  skin,  69 
mucosum  of  skin,  69 
Reticular  cartilage,  57 
Reticulum,  40 

adenoid,  167 
Retrograde  changes,  20 
Retzius,  lines  of,  80 
Ringing  mounts,  34,  198 
Rods,  contractile,  63 
Rogers'  stage-micrometer,  8 
Root-sheath  of  hair,  71 
Rouge,  optician's,  199 

Sacs,  air,  100 
Salamander,  201 
Salivary  abdominal  gland,  154 
corpuscles,  87,  41 
glands,  157 

Salt  solution,  normal,  199 
Salter,  incremental  lines  of,  79 
Sarcolemma,  63 
Sarcous  element,  65 
Satterthwaite,  fat  columns  of,  70 
Scalp,  hair  from,  74 
Schrauer  microtome,  14 
Schwann,  white  substance  of,  180 
Sebaceous  gland,  74,  155 
Sebum,  74 
Secretion  of  succus  entericus,  88 

pancreatic,  159 
Section  cutting,  9 

cutting,  free-hand,  10 
cutting,  with  Stirling  micro- 
tome. 12 
lifter,  32 
needle,  27 
spoon,  32 

Sediments,  urinary,  199 
Septa,  interlobular,  of  lung,  100 
Septum  narium,  56 
Serous  gland,  159 

surfaces,  pencilling  of,  163 
Sharpening  knives,  16 
Sharpey's  fibres,  59 
Sheath,  dentinal,  78 
Sheep,  spinal  cord  of,  187 
Shellac  varnish,  198 
Silk  fibres,  37 
Silver,  albuminate  of,  164 

nitrate  of,  26 

solution,  26 

staining  solution,  200 
Silvered  mesentery,  42 
Skeletal  muscle,  63 
Sketching  from  microscope,  8 
Skin,  68 


INDEX. 


215 


Skin,  chamois,  34 

practical  demonstration,  74 
staining  of,  74 
sudoriferous  glands  of,  72 
Slides,  labelling,  34 
Small  intestine,  88 
Smooth  muscle,  62 
Soda,  acetate  of,  199 
Soldering  with  paraffin,  18 
Solitary  "glands,"  91 

lymphatics,  88 
Solution,  chromic  acid,  22 
eosin,  26 
normal  salt,  180 
osmic  acid,  200 
picric  acid,  26 
silver,  26.  200 
Space,  subarachnoid,  191 

subdural,  191 
Spaces,  interglobular,  78,  82 

venous,  173 

Special  connective  tissues,  61 
sense,  nerves  of,  181 
Specimen,  permanent,  33 

trays,  34 

Spheroidal  cells.  47 
Spider  cells,  183 
Spinal  cord,  185 

cord,  central  canal  of,  186 
cord,  commissures  of,  185 
cord,  diagram  of,  185 
cord,   funiculus  cuneatus  of, 

187 
cord,    funiculus    gracilis    of. 

187 

cord,  lymph  spaces  of,  190 
cord,  nerve  roots  of,  185 
cord  of  domestic  animals,  187 
cord,  practical  demonstration, 

186 
cord,   physiological  areas  of, 

185 
cord,  substantia  gelatinosa  of, 

185 

nerve,  185 
Spiral  tubule,  122 
Spirals  from  tea  leaf,  38 
Spleen,  173 

Malpighian  bodies  of,  173 
practical    demonstration    of, 

173 

pulp,  173 

supernumerary,  174 
Spoon,  section,  32 
Spores,  fermentation,  38 

vegetable,  38 
Spot,  germinal,  146 
Squamous  epithelium,  41 
Squibb's  chloroform,  197 
Stage  micrometer,  8 
Staining  agents,  25 

carmine  and  picric  acid,  31 


Staining,  double,  21,  29 

eosin,  203 

fluid,  borax-carmine,  26 

fluid,  haema.,  25 

fresh  tissue,  25 

haBma.,  27 

haema,  and  eosin,  27 

nigrosin,  203 

osmic  acid  in  nerve  tissue, 
180,  200 

silver,  163 

solution,  silver,  200 

Weigert's  nerve,  200 
Starch,  38 

Stars  of  Verheyen,  126 
Stellate  cells,  47,  50 
Sternum,  163 
Stirling  microtome,  12 
Stirling's  processes,  22 
Stomach,  83 

and  intestines,  83 
hardening  of,  87 
of  dog,  86 
Stomata,  44,  67,  164 
Straight  kidney  tubule,  124 
Stratified  epithelium,  41 
Stratum  corneum  of  skin,  68 

granulosum  of  skin,  68 

lucidum  of  skin,  68 
Striae,  dentinal,  82 
Striated  muscle,  63 
Stroma  of  ovary,  144 
Stropping  knives,  18 
Structural  elements,  35 
Structure,  glandular,  157 
Subarachnoid  space,  191 
Subcutaneous  cellular  tissue,  70 
Subdural  space,  191 
Sublingual  gland,  157 
Sublobular  veins,  106 
Submaxillary  gland,  158 
Substance,  white  of  Schwann,  180 
Substances,  extraneous,  37 
Substantia  gelatinosa,  185 
Succus  entericus,  88 
Sudoriferous  gland,  73,  154 
Sulci,  191 

Sulphate  of  copper,  22 
Supernumerary  spleen,  174 
Suprarenal  bodies,  120 
capsule,  150 

capsule,  practical  demon- 
stration of,  150 
Sweat  glands,  number  of,  74 

tubes,  154 

Sympathetic  system,  181 
System,  cerebro-spinal,  180 

Haversian,  59 

lymphatic,  161 

sympathetic  nervous,  181 

the  nervous,  180 

vascular,  of  kidney,  125 


216 


INDEX. 


Tactile  corpuscles,  71 

Tailed  cells  from  ureter  and  pelvis  of 

kidney,  140 
Tallow,  bayberry,  22 
Tea  leaf,  38 

Teased  nerve  fibres,  180 
Teasing,  9 

glandular  structures,  159 
Teeth,  78 

decalcification  of,  80 
development  of,  80 
foetal,  80 

grinding  sections  of,  80 
practical  demonstration  of,  80 
Telegraphic  cable,  181 
Teadon, 52 

diaphragmatic,  163 
Terminal  bronchi,  97,  101 
Termini,  nerve,  181 
Tesselated  epithelium,  42 
Thermal  currents,  36 
Thoracic  cavity,  162 

duct,  162 
Thyinus  body,  hardening  of,  177 

body,  Hassal's  corpuscles  in, 

179 

Tissue,  adenoid,  61,  167 
adipose,  54 
adipose  in  bronchi,  99 
areolar,  51 
cicatricial,  146 
connective,  51 
connective  of   nerve  trunks, 

181 

drainage,  161 
embryonic,  62 
fat,  54 
fibrous,  51 
fresh,  20 
hardening  of,'20 
muscular,  62 

sustentacular  of  brain,  183 
white  fibrous,  51 
yellow  elastic,  52 
Tissues,  dehydration  of,  28 

selective  power  of,  25 
special  connective,  61 
translucency  of,  28 
Tongue,  158 

epithelium  of,  41 
Tooth,  canine,  81 
Tortuosity  of    hepatic   cell-columns, 

115 
TrabeculaB  of  lymph  nodes,  167 

splenic,  173 
Trachea,  56,  158 
Tract,  crossed  pyramidal,  183 

genito-urinary,  135 
Tracts,  direct  cerebellar,  185 
direct  pyramidal,  185 
lateral,  185 
Transitional  epithelium,  41 


Transmitted  light,  9 
Transverse  fissure  of  liver,  106 
Trigone,  142 
Tripolar  cells,  50 

nerve  cells,  181 
True  skin,  69 
Tube,  bronchial,  94 

Eustachian,  58 
Tubular  glands,  153 

membrane,  181 
Tubule,  Bellini's,  124 

collecting,  124 

gastric,  83 

Henle's,  123 

proximal  convoluted,  122 

spiral,  122 

straight,  123 

Tubules,  uriniferous,  121 
Tumors,  201    • 
Tunica  albuginea,  144,  147 
Turpentine,  197 
Typical  artery,  66 

cell,  39,  146 

Unipolar  cells,  50 

nerve  cells,  181 
Ureter,  120 

mucosa  of,  141 

Urinary  casts,  preserving,  199 
deposits,  135 
organs,  135 
Urine,  bacteria  in,  37 
cells  in,  143 
course  of,  in  kidney,  122,  126, 

127 

Uriniferous  tubules,  122 
Uterus,  mucosa  of,  136 

Vacuolated  cells,  vaginal,  136 
Vagina,  cul-de-sac  of,  136 

mucosa  of,  136 
Valves  of  lymph  paths,  164 
Variation  of  cell  forms,  40 
Varicosities  of  nerves,  181 
Varnish,  asphaltum,  198 
black,  198 
dammar,  197 
shellac,  198 
Vascular  supply  of  lung,  100 

supply  of  lymph  nodes,  167 
system  of  spleen,  173 
system  of  thymus  body,  179 
Vegetable  spores,  38 
Vein,  bronchial,  98 

portal,  106 
Veins,  66 

central,  106 

efferent,  of  lymph  nodes,  167 

hepatic,  106 

inteiiobular,  106 

intralobular,  106 

sublobular,  106 


INDEX. 


217 


Venous  spaces  of  spleen,  173 
Venulae  rectaB,  126 
Venules,  66 

"Verheyen,  stars  of,  126 
Vesicle,  germinal,  146 
Vesicles,  air,  100 
Villi  of  intestine,  88 
Viscera,  chylopoietic,  106 
Vital  movements,  37 
Voluntary  muscle,  63 

Wall,  cell,  39 

uterine,  136 

Walls  of  stomach  and  intestines,  83 
Water,  boiled,  163 

distilled,  163 

lenses,  36 

of  Ayr  hone,  17 
IVax,  bayberry,  22,  201 


Weigert's  nerve  staining,  186,  200 

Wood,  coniferous,  38 

Wenham  objective,  2 

Wheat  starch,  38 

White  blood. corpuscles,  49 
commissure,  185 
fibrous  tissue,  51 
matter  of  brain,  191 
substance  of  Schwann,  180 

Xiphoid  appendix,  58 
Xylol  balsam,  197 

Yellow  elastic  tissue,  52 

Zinc  cement,  198 
Zona  pellucida,  146 
vasculosa,  144 


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